Expand and explain HTML and CSS. Mention the role of each one in web pages. Imagine how a page without CSS will look like.
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Answer:
That’s usually the first question that gets asked about web standards. You can accomplish content, styling and layout just using HTML — font elements for style and HTML tables for layout, so why should we bother with this XHTML/CSS stuff? Tables for layout, etc. is how it used to be done in the bad old days of web design, and many people still do it like this (although you really shouldn’t), which is one of the reasons why we created this course in the first place. We won’t be covering such methods in this course. Here are the most compelling reasons for using CSS and HTML over outdated methods:
Efficiency of code: The larger your files are, the longer they will take to download, and the more they will cost some people to view (some people still pay for downloads by the megabyte.) You therefore don’t want to waste your bandwidth on large pages cluttered up with styling and layout information in every HTML file. A much better alternative is to make the HTML files stripped down and neat, and include the styling and layout information just once in a separate CSS file. To see an actual case of this in action, check out the A List Apart Slashdot rewrite article where the author took a very popular web site and re-wrote it in XHTML/CSS.
Ease of maintenance: Following on from the last point, if your styling and layout information is only specified in one place, it means you only have to make updates in one place if you want to change your site’s appearance. Would you prefer to update this information on every page of your site? I didn’t think so.
Accessibility: Web users who are visually impaired can use a piece of software known as a “screen reader” to access the information through sound rather than sight — it literally reads the page out to them, and it can do a much better job of helping people to find their way around your web page if it has a proper semantic structure, such as headings and paragraphs. In addition keyboard controls on web pages (important for those with mobility impairments that can't use a mouse) work much better if they are built using best practices. As a final example, screen readers can’t access text locked away in images, and find some uses of JavaScript confusing. Make sure that your critical content is available to everyone.
Device compatibility: Because your HTML/XHTML page is just plain markup, with no style information, it can be reformatted for different devices with vastly differing attributes (eg screen size) by simply applying an alternative style sheet — you can do this in a few different ways (look at the [mobile articles on dev.opera.com] for resources on this). CSS also natively allows you to specify different style sheets for different presentation methods/media types (eg viewing on the screen, printing out, viewing on a mobile device.)
Web crawlers/search engines: Chances are you will want your pages to be easy to find by searching on Google, or other search engines. A search engine uses a “crawler”, which is a specialized piece of software, to read through your pages. If that crawler has trouble finding the content of your pages, or mis-interprets what’s important because you haven’t defined headings as headings and so on, then your rankings in relevant search results will probably suffer.
It’s just good practice: This is a bit of a “because I said so” reason, but talk to any professional standards-aware web developer or designer, and they’ll tell you that separating content, style, and behaviour is the best way to develop a web application.
Markup, the basis of every page
HTML and XHTML are markup languages composed of elements, which contain attributes (some optional and some mandatory.) These elements are used to mark up the various different types of content in documents, specifying what each bit of content is supposed to be rendered as in web browsers (for example headings, paragraphs, tables, bulleted lists etc.)
Elements define the actual content type, while attributes define extra information about those elements, such as an ID to identify that element, or a location for a link to point to. You should bear in mind that markup is supposed to be as semantic as possible, ie it is supposed to unambiguously describe the function of the content. Figure 1 shows the anatomy of a typical element.
A typical HTML element
Explanation:
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