Martin Kruliš, Martin Nečaský 29. 10. 2015 by Martin Kruliš (v1.1)1

by Martin Kruliš (v1.1) 1

Hypertext Markup Language

Martin Kruliš, Martin Nečaský

29. 10. 2015


HTML = Hypertext Markup Language◦ World Wide Web's markup language◦ Language for describing the structure of Web

pages

Web Page◦ Semi-structured document

Form of structured data with non-formal structure model

Basically a plain text interleaved by markers (tags) that impose some form of internal structure

◦ Structure denoted in a form of HTML markup

29. 10. 2015

What is HTML?

by Martin Kruliš (v1.1) 329. 10. 2015

What is HTML?

<!DOCTYPE html><html lang="en"> <head> <title>Simple web page</title> </head> <body> <h1>Simple web page</h1> <p>This is a <em>web page</em> with <a href="http://whatwg.org/html">HTML5</a> markup.</p> </body></html>


HTML Document◦ Is structured as a tree

HTML syntax is in fact an infix serialization of the tree

Browsers represent the tree in Document Object Model (DOM), which can be manipulated with JavaScript

◦ Various types of nodes Elements, text, attributes, comments, …

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HTML Syntax


DOM Tree Example<html> <body> <h1>DOM Example</h1> <p> Document Object Model is an API … </p> <img src="url" alt="text"> ... </body></html>

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HTML Syntax

body

h1 p img

Document

src

DOM Example Document Object Model

…

alt

html

…


HTML Element◦ Represents a fragment of a web page

Gives semantic meaning to its content◦ Opening and closing tags work as parentheses for

the content (i.e., what falls into the element) Content-less elements may omit closing tag Elements may not cross-overlap

◦ Attributes Name-value pairs specified in opening tag Values are optional and they are optionally enclosed

in single or double quotes (recommended) Quotes are mandatory if the value contains ",', <, or >

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HTML Syntax


Comments◦ Enclosed in ◦ Not displayed when page is rendered

Entities◦ &entity-name;◦ Provide a way to encode special characters◦ <, >, &, " - <, >, &, "◦ - non-braking space◦ Numerically represented characters ü - “ü”

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HTML Syntax


Evolution of HTML

HTML 2.0

HTML 3.2

HTML 4.01

XHTML 1.0

XHTML 1.1

1997

1995

1999

2000 2001

HTML 5 XHTML 2 2010

www.whatwg.org

2014

XML 1.0

www.w3.org


WhatWG◦ http://whatwg.org/html◦ "Living Standard" (see Last Updated)

W3C◦ http://www.w3.org/TR/html5/◦ Formal standardization process

Stages of W3C a document (draft, CR, R)

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Evolution of HTML

http://whatwg.org/html

http://www.w3.org/TR/html5/


Current World Wide Web is sometimes referred to as Web of Documents◦ HTML as a format for representing documents

published on the Web◦ URLs as unique global identifiers of documents◦ HTTP for localization and accessing documents by

their URLs◦ Hyperlinks between documents to link related

documents on the Web

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Web of Documents


Web of Documents

Web Page

http://example.com/page.html

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...

Web Page

http://...


Hyperlink Elements◦ Links to external resource, which are exposed to

user of the current document as means to browse

<a href="http://www.google.com">Google</a> Attribute href specifies URL of linked resource Content is visible to user (text or any inline

elements)◦ Identifying fragment of a web page

<p id="Para2"> ... </p> Is then referenced by fragment part of an URL

<a href="#Para2">...</a> <a href="http://www.page.com#Para2">...</a>

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Hyperlinks


Markup in HTML(5) Body◦ Text level semantics elements

Denote parts of the text in a HTML document witha specific semantics

◦ Sectioning content◦ Grouping content◦ Tables, forms◦ External sources (images)◦ Hyperlinks◦ …

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HTML Body


Text Level SemanticsElement Description

em Represents stress emphasis of its content. The level of stress is given by the level of nesting of particular em elements

strong Represents strong importance of its content.

small Represents a side comment.

s Represents no longer relevant or accurate content.

cite Represents a title of a work (book, article, game, software, song, opera, ...).

abbr Represents an abbreviation or acronym, optionally with its expansion in title attribute.

data Represents its content enriched with its machine readable notation in value attribute.

time Represents its content which is a determination of time with machine readable notation in datetime attribute.

i Represents its content in a manner indicating different quality of text

b Represents its content to which attention is being drawn

br Represents a line break


Defining Internal Structure of Document Body◦ Content of document is divided into sections◦ Sections are divided to subsections◦ section element – a generic section◦ article element - self-contained main section

Independently distributable and reusable E.g., a blog post or a newspaper article

◦ aside element – separate section Marginal content E.g., a did-you-know aside box

◦ nav element – section containing navigation links

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Sectioning Content


Sectioning Content<article> <p>This article summarizes technologies ...</p> <nav> <a href="#html">HTML</a><a href="#css">CSS</a> </nav> <section id="html"> <p>We will start with HTML.</p> <section><p>First, we will go to history.</p></section> <section><p>Then, we will deal with actual 5.0.</p></section> </section> <aside> <p>Did you know that SGML is a predecessor of HTML?</p> </aside> <section id="css"><p>CSS is the second technology.</p></section> <nav> <div><a href="...">Home</a><a href="...">Contact</a></div> </nav></article><article>Another article</article>


Headers and Footers◦ Within a section or for the whole document◦ header element

Distinguishes header of the nearest section (hierarchically)

Intended (but not required) to contain heading elements (h1 – h6)

◦ footer element Distinguishes footer of the nearest section

(hierarchically) Usually contains copyrights, author info, etc.

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Headers and Footers


Sectioning Content<article> <header> <h1>NSWI117 – Summary of technologies</h1> </header> <section> <header> <h1>HTML</h1> </header> <p>We will start with HTML.</p> </section> <footer> <nav> <div><a href="...">Home</a> <a href="...">Contact</a></div> </nav> </footer></article>


Heading Elements h1 – h6◦ Before HTML5

Six levels of importance (rank) <h1> most important (highest), <h6> least important

◦ Headings in HTML5 Combined with sectioning <section>, <article>, … Attempt to keep some backwards compatibility

Quite difficult to realize though Each section has its own heading hierarchy First heading element in a section is the main

heading of that section (no matter its rank)

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Headings


Outline Algorithm◦ First heading (any of <h1>…<h6>) in the section is

the heading of the section◦ Subsequent headings create new implicit sections

Headings of the same or higher rank implicitly close current section and start another one

Headings of lesser ranks open implicit subsections Implicit subsections are closed when ancestor

explicit section is closed

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Section Headings in HTML5


Section Headings Example<body> <h1>NSWI142 - ...</h1> <p>At this page, ...</p> <h2>HTML</h2> <p>About HTML ...</p> <h3>HTML History</h3> <h3>HTML Today</h3> <h2>CSS</h2> <p>About CSS ...</p></body>

Sections Structure

• NSWI142 - …• HTML

• HTML History• HTML Today

• CSS


Section Headings Example<body> <h1>NSWI142 - ...</h1> <p>At this page, ...</p> <section> <h2>HTML</h2> <p>About HTML ...</p> <section> <h3>HTML History</h3> </section> <section> <h3>HTML Today</h3> </section> </section> <section> <h2>CSS</h2> <p>About CSS ...</p> </section></body>

Sections Structure



• CSS


Section Headings Example<body> <h1>NSWI142 - ...</h1> <p>At this page, ...</p> <section> <h1>HTML</h1> <p>About HTML ...</p> <section> <h1>HTML History</h1> </section> <section> <h6>HTML Today</h6> </section> </section> <section> <h1>CSS</h1> <p>About CSS ...</p> </section></body>

Sections Structure



• CSS


Outline Algorithm◦ Is not currently implemented in graphical

browsers!

How to Fix The Problem◦ Use single heading in each section

Use <h1> everywhere Express importance by <section> nesting

Or use appropriate heading based on nesting level E.g., <h3> in 2nd level (<section><section>…)

◦ Additional help from CSS may be required

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Section Headings in HTML5


Grouping Content

Element Description

p Represents a paragraph

pre Represents a block of preformatted text

div Element with no special meaning (generic container)

main Represents a block with a dominant content

ul Represents an unordered list

ol Represents an ordered list

li Represents a list itemThis is not a complete list!


List Example

<ul> <li>First item</li> <li>Second item: <ol> <li>HI</li> <li>HELLO</li> <li>GOOD MORNING</li> </ol> </li> <li>Third item</li></ul>

• First item• Second item:

1. HI2. HELLO3. GOOD MORNING

• Third item


Tables

Element Description

table table

thead table head

tbody table body

tfoot table footer

tr table row

th table head cell

td table data cell

The <thead>, <tbody> and <tfoot> table division may be omitted for simple tables

2829. 10. 2015by Martin Kruliš (v1.1)

Table Example<table> <thead> <tr> <th>Name</th><th>Email</th><th>Address</th> </tr> </thead> <tbody> <tr> <td>Joe White</td> <td>[email protected]</td> <td>Lloyd Ave, Boston</td> </tr> <tr> <td>Bill Black</td> <td>[email protected]</td> <td>---</td> </tr> </tbody></table>

Name Email Address

Joe White [email protected]

Lloyd Ave, Boston

Bill Black [email protected] ---


Spanning Table Cells◦ Virtually grouping content of multiple logical cells

◦ Attribute colspan of element td and th Spans selected cell over several following columns Specifies the number of columns taken by the cell

◦ Attribute rowspan of element td and th Spans selected cell over several following rows Specifies the number of rows taken by the cell

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Irregular Tables


Irregular Tables<table> <tr> <td colspan="2">Adults</td> <td>2</td> </tr> <tr><td>Adult 1</td><td>34</td><td rowspan="2">2</td></tr> <tr><td>Adult 2</td><td>32</td></tr> <tr> <td colspan="2">Children</td> <td>3</td> </tr> <tr><td>Child 1</td><td>4</td><td>1</td></tr> <tr><td>Child 2</td><td>8</td><td rowspan="2">2</td></tr> <tr><td>Child 3</td><td>12</td></tr></table>

Adults 2

Adult 1 342

Adult 2 32

Children 3

Child 1 4 1

Child 2 82

Child 3 12


HTML Form◦ Component of web page composed of UI controls◦ User can interact with form controls

Adding text, selecting options, clicking on buttons, … Data provided by user can be processed by a script

By Javascript in the browser or by a server script

Element <form>◦ Attribute method – HTTP method used for transfer

post – data are transferred in HTTP request body get – data are encoded in URL (query part)

◦ Attribute action – URL where the data are sent to

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Forms


Form Controls◦ input

Basic input controls Various types based on input attributes

◦ textarea Input for longer (multi row) texts

◦ select Selection list with options

◦ button Submit or reset button

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Forms


Forms Example

<form method="get" action="http://www.example.org/newcustomer.php"> Name: <input name="name" ... > Phone: <input name="phone" ... > Preferred delivery time: <input name="time" ... > Comments: <textarea name="comments"></textarea> <button type="submit">Submit Order</button></form>

Submit button works as a link to an assembled URL:http://www.example.org/newcustomer.php ?name=John+Smith&phone=555-1234& time=5pm&comments=unleashed+dog+at+house


Element <input> - basic form input field◦ Attribute name specifies identifier of the field

For script which processes the data on the server◦ Attribute type specifies type of the input

text – input is one line of text + attribute maxlength – maximal text length

password – same as text, but obscures input with * radio – exclusive choice (radio buttons) from set of

fields with the same name + attribute value – value send to server (when selected) + attribute checked="checked" – default choice

checkbox – multiple choice, similar logic as radio

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Forms


Element input Example<form method="post" action="http://www.example.org/script.php"> <p> Name: <input type="text" name="fullName" maxlength="5"><br> Password: <input type="password" name="password"><br> </p> <p>Age:<br> 0-18: <input type="radio" name="age" value="0"><br> 19-65: <input type="radio" name="age" value="19"><br> 66-*: <input type="radio" name="age" value="65"><br> </p> <p>Product:<br> <input type="checkbox" name="product" value="BMW">BMW<br> <input type="checkbox" name="product" value="AUD">Audi<br> <input type="checkbox" name="product" value="POR">Porsche<br> </p> </form>


Element <input>◦ Attribute type specifies type of the input

submit – submission button + attribute value contains displayed button value

reset – reset button + attribute value contains displayed button value

hidden – submitted value hidden to user Fixed value, user cannot change it

file – file submission Browser allows selecting file on local disk, which is then

uploaded to the server

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Forms


Element input Example

<form method="post" action="http://www.example.org/script.php"> <p> Name: <input type="text" name="fullName" maxlength="5"><br> Password: <input type="password" name="password"><br> </p> <input type="hidden" name="requestCode" value="H38aJJJ"> <input type="submit" value="Submit Form"> <input type="reset" value="Reset Form"> </form>


Element <input>◦ The control element might be further specified◦ maxlength attribute

Maximum number of characters allowed in a text field

◦ size attribute Number of characters visible in a text field

◦ value attribute Specifies default/selected field value

◦ disabled="disabled" attribute Specifies that field is disabled when form loads

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Forms


Element input Example

<form ... > <input name="full_name" maxlength="32" size="16" value="Martin Nečaský" disabled title="First name followed by family name."> <button type="submit">Submit</button></form>


Element <select>◦ List of options user selects from◦ Sub-element <option>

Content is shown to the user Attribute value – submitted value Attribute selected="selected" – default value

◦ Attribute multiple="multiple" Allows user to select more values

◦ Attribute size Number of options (rows) displayed at once If size=1, the list is shown as drop-down-list box

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Forms


Element select Example

<form ... > <p>Product:<br> <select name="product" size="4" multiple="multiple"> <option value="BMW">BMW</option> <option value="AUD" selected="selected">Audi</option> <option value="MER">Mercedes</option> <option value="SKO">Skoda</option> <option value="CHE">Chevrolet</option> <option value="TOY">Toyota</option> <option value="FOR">Ford</option> </select> </p> </form>


Additional Form Elements◦ Making the form structured and better readable◦ <fieldset> element

Groups logically related fields◦ <legend> element

Caption for a <fieldset> element◦ <label> element

Caption for a control element (e.g., <input> element)

◦ title attribute Balloon tip hint for a field (This is attribute may be used with any HTML

element)

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Forms


Form Elements Example<form ... > <p><label>Name: <input ... ></label></p> <fieldset> <legend>Contact information</legend> <p><label>Phone: <input ... ></label></p> <p><label>Email: <input ... ></label></p> </fieldset> <fieldset> <legend>Timing</legend> <p> <label for="time">Preferred delivery time:</label> <input id="time" title="Time in hh:mm format." ... > </p> </fieldset> <p><label>Comments: <textarea></textarea></label></p> <button>Submit Order</button></form>


Element <input> New HTML5 Types◦ search - search query field◦ tel - phone number field◦ url - absolute URL (e.g., page address) field◦ email - email address field◦ date, time, datetime - date/time field◦ number – number (entered as text) field◦ range - number (entered by slide bar) field◦ color – color selection field◦ Unsupported types are treated as text inputs

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Forms in HTML5


HTML5 <input> Attributes◦ autocomplete attribute

Turns automatic completion of a field on/off◦ autofocus attribute

Turns the focus to the field when the page loads◦ pattern attribute

Regular expression for field value validation◦ placeholder attribute

Hint for the user to help with filling the field◦ required attribute

Field value is mandatory for form submission

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Forms in HTML5


Element select Example

<form ... > <input name="phone" autocomplete="off" autofocus="autofocus" pattern="[0-9]{9}" placeholder="Fill in your 9-digit phone number" required="required"> <button>Submit</button></form>


When Form Is Submitted …◦ Data are encoded into HTTP request made for

selected URL using given method (GET/POST) In case of GET request, the data are encoded to URL

◦ enctype attribute of element <form> specifies the format of the encoded data (for POST requests) application/x-www-form-urlencoded multipart/form-data text/plain

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Submitting Forms


Submitting Forms Example

<form method="post" action="?" enctype="..."> Full Name: <input name="fullname" type="text"><br> Gender: <input name="gender" type="radio" value="M"> male, <input name="gender" type="radio" value="F"> female<br> <input name="student" type="checkbox" value="1"> student<br> <input type="hidden" name="tag" value="#a&Hx9%"> <button type="submit">Submit</button></form>


application/x-www-form-urlencoded

fullname=Martin+Kruli%C5%A1&gender=M&student=1&tag=%23a%26Hx9%25

text/plain

fullname=Martin Krulišgender=Mstudent=1tag=#a&Hx9%

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multipart/form-data-----------------------------88242493723271

Content-Disposition: form-data; name="fullname"

Martin Kruliš

-----------------------------88242493723271

Content-Disposition: form-data; name="gender"

M

-----------------------------88242493723271

Content-Disposition: form-data; name="student"

1

-----------------------------88242493723271

Content-Disposition: form-data; name="tag"

#a&Hx9%

-----------------------------88242493723271--

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Element <img>◦ Include image in the document contents◦ Attribute src – the URL of an image to be loaded◦ Attributes width and height - image size in pixels

It is a good practice to let the browser know the size before the image is loaded (or if it fails)

◦ Attribute alt – alternative textual representation Briefly describes, what the image shows Used, when the image loading fails

◦ Attribute title – same as in form controls

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Images


Additional Information about The Document ◦ Inside element <head>◦ <title> - document title or name

Identify document for users (browser window caption)◦ <base> - URL base for resolving relative addresses◦ <link> - links document to other resources

Cascading stylesheet files, for instance◦ <style> - embeds style information inside

document Contents is written in CSS stylesheet syntax

◦ <meta> - additional metadata and HTTP supplements Description, keywords, document author, …

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Document Metadata


Document Metadata

<html> <head> <title>Technologies for …</title> <base href="http://www.ksi.mff.cuni.cz/index.html">

<link rel="stylesheet" href="default.css"> <style type="text/css"> body { font-size: 12pt; } </style>

<meta name="keywords" content="html, example"> <meta http-equiv="content-type" content="text/html; charset=utf-8"> </head></html>

In HTML5, this particular construction can be shorten to <meta charset="utf-8">


HTML5 Definition of Link◦ Link represents relationship of particular type

between current document and other web resource

◦ Syntactically defined by elements <link> and <a>◦ Two kinds of links (according to HTML5 spec.)

Links to external resources Augment/further specify current document

Hyperlinks Exposed to the user to navigate between resources

The kind depends on the element used and on the relationship type (attribute rel)

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More on Links


Link Specification◦ href attribute

URL of resource linked by relationship◦ rel attribute

Type of relationship◦ media attribute

Media linked resource applies to E.g., print, screen, all

◦ type attribute MIME type of linked resource text/html, application/xhtml+xml, text/css, application/pdf

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More on Links


More on LinksLink type link a Description

alternate H H Alternate representation of current document

author H H Author of document

icon ER - Icon representing current document

stylesheet ER - Stylesheet for current document

licence H H Copyright license covering current document

first H H First document of a series current document is part of

last H H Last document of a series current document is part of

next H H Next document in a series current document is part of


More on Links<html> <head> <title>NSWI142 – Materials</title> <link rel="stylesheet" href="default.css" type="text/css" media="screen"> <link rel="stylesheet" href="default-print.css" type="text/css" media="print"> <link rel="alternate" href="materials.pdf" type="application/pdf" media="print"> </head> <body> <footer>Author: <a href="http://www.ksi.mff.cuni.cz/~krulis" rel="author"> Martin Kruliš</a> </footer> </body></html>


Differences◦ No sense to go through particular differences in

this lecture◦ See http://www.w3.org/TR/html5-diff

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HTML Markup – 4.01 vs. 5

http://www.w3.org/TR/html5-diff


Discussion