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HTML
Standards & Compliance
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Minimum Required HTML tags:
<html>
<head>
<title>
</title>
</head>
<body>
</body>
</html>
(must go in this order!)
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HTML document
• An HTML document can be created in any plain text editor like TextEdit on a Mac or Notepad on a PC and saved as anyname.html or anyname.htm
• .html file extension is preferred
• Most HTML tags have opening and closing tags
• Any extra lines or extra character spacing will be ignored
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HTML tags
• Tags can be nested
<p><em> hello</em></p>
but must be nested in the correct order
• Tags were case insensitive (upper, lower or mixed) although the newer standards of XHTML now require all lower case (except in the DTD)
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Additional required tags shown in bold required for validation:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd"><html>
<head>
<title>
title goes here
</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> </head>
<body>
<h1>
welcome to my webpage
</h1>
<p>
<img src="http://www.vegas.com/image.jpg" alt="vegas image">
</p>
</body>
</html>
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Dreamweaver auto adds required code
Authoring tools like Dreamweaver automatically put the required DTD and meta tag based on your preferences and HTML document version you specify when creating a new webpage
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DTDs defined
• When authoring a document that is HTML or XHTML, it is important to Add a DTD or Doctype declaration
• The declaration must be exact (both in spelling and in case) to be understood
• DTD declaration is often called "Doctype” or “DTD”
DTD example:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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Why DTD is needed?
• Browsers, tools, and devices which process HTML documents, such as Web browsers, need to know which DTD an (X)HTML document is actually using
• This is a critical piece of information needed by browsers or other tools processing the document
• If you hand code your pages make sure to add the DTD
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Other reasons to specify a doctype?
• Allows you to use tools such as a markup Validator to check the syntax of your (X)HTML (and hence discovers errors that may affect the way your page is rendered by various browsers)
• Such tools and browsers won't be able to work optimally if they do not know what kind of document or what version of HTML you are using
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And even more reasons to specify a doctype?
• With most families of browsers, a doctype declaration or DTD will make a lot of guessing unnecessary
• Will trigger a "standard" parsing mode, where the understanding (and, as a result, the display) of the document is not only faster, it is also consistent and free of any bad surprise that documents without doctype will create
• Very important for “new” and “future” devices like cell phones which will be displaying web pages
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Next, are some of the list of recommended declarations that you can use in your Web documents
Refer to the following URL for a list of valid DTD's
http://www.w3.org/QA/2002/04/valid-dtd-list.html#DTD
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HTML 4.01 - Strict, Transitional, Frameset:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
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XHTML 1.0 - Strict, Transitional, Frameset:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
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XHTML 1.1 - DTD:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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The most widely used DTD by professional Web designers is
XHTML 1.0 Transitional
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
We will be using this version of XHTML during our class
When you create a new document in DW File>New make sure
you specify the DocType: XHTML 1.0 Transitional
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The term “Transitional” in relation to DTD versions
• Means you are allowed to use some of the legacy HTML
• May be hard to know what tags are considered legacy vs obsolete
• Should always validate your page to test for compliance
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Some argue the most widely supported DTD is 4.01
4.01 is no longer recommended for authoring since it is an old versions of HTML and represents outdated html and pre CSS
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HTML Deprecated vs Obsolete
• Deprecated means outdated and may soon become obsolete
• Obsolete means it is no longer supported and may not be recognized (by browsers or interpreters)
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Deprecated
• A deprecated element or attribute is one that has been outdated by newer constructs
• Deprecated elements may become obsolete in future versions of HTML
• User agents (like browsers) should continue to support deprecated elements for reasons of backward compatibility
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Obsolete
• An obsolete element or attribute is one for which there is no guarantee of support by a user agent
• Obsolete elements are no longer defined in the specification
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DEPRECATED example
The following HTML page illustrates the use of the deprecated attributes, deprecated in XHTML
It sets the background color of the canvas to white, the text foreground color to black, etc.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><HTML><HEAD> <TITLE>A study of population dynamics</TITLE></HEAD><BODY bgcolor="white" text="black" link="red" alink="fuchsia" vlink="maroon"> ... document body...</BODY></HTML>
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CSS Cascading Style Sheets
• In XHTML the presentational attributes of BODY have been deprecated and replaced with CSS
• CSS now the preferred way to specify a document's presentation
<style type="text/css">body {
background-color: black; }
</style>
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Older Browsers that don't support CSS
• Older browsers, before Netscape 4.0 and Internet Explorer 4.0, either don't support CSS at all or do so inconsistently
• For these browsers you can still control the style by using HTML if absolutely necessary
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Validating HTML pages
• Webpage's can and should be valididated (tested)
• To further promote the reliability and fidelity of communications on the Web, W3C has a
W3C Markup Validation Service at
http://validator.w3.org
• Dreamweaver also allows you to validate from within its program File>Validate>Markup
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Benefits to validating
• Web pages will work more consistently and on a wider variety of browsers
• Web pages load faster
• Will be better supported on new devices being used to view web pages
• More accessible to the visually impaired who use aural screen readers (<img> alt and src required for strict)
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XHTML requirements
• Stricter standards than older HTML
• Legacy HTML has been removed
• To become validated you must have a fully compliant, standardized Web site
• Should always validate your page to test for compliance
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XHTML requirements
• Start each page with DOCTYPE
• The open <html> should come after the DOCTYPE
• Include both <head> and <body> elements
• Always include a <title> element within <head> element
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XHTML requirements
• <title>, <meta>, and <style> elements must all be within the <head> element
• Only put <block> elements inside the <body> element
• All inline elements and text need to be inside another block element before they can go in the <body> element
• Only put text and other inline elements within an inline element, no block elements
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XHTML requirements
• Keep block elements out of your <p> element
• Requires inline elements (like <img>) to be nested inside block elements (like <p>)
• Use paragraphs for inline elements and for text
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Inline elements must go in block elements
• Inline elements include <q>, <a>, <em>
• Block elements include <p>, <h1>, <h2>, <h3>, etc
• Don’t put block elements inside other block elements or inside inline elements
• Example of a block element containing an inline element
<p><img src="http://www.cnn.com/image.jpg" alt="Image of people waiting for food">
</p>
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XHTML requirements
• The blockquote element requires one or more block elements inside it
• You can put inline elements and text within a blockquote element but there must be another block element within it
<blockquote><p>Text goes here</p></blockquote>
• But not the block element <blockquote>
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XHTML requirements
• Empty tags (single tags) must be closed using /
Image
<img src="url" />
Line Break
<br />
-end
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