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XHTML HowTo

How W3Schools Was Converted To XHTML

W3Schools was converted from HTML to XHTML the weekend of 18. and 19. December 1999, by Hege Refsnes and Ståle Refsnes.

To convert a Web site from HTML to XHTML, you should be familiar with the XHTML syntax rules of the previous chapters. The following steps were executed (in the order listed below):

A DOCTYPE Definition Was Added

The following DOCTYPE declaration was added as the first line of every page:

<!DOCTYPE html PUBLIC
"-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

Note that we used the transitional DTD. We could have chosen the strict DTD, but found it a little too "strict", and a little too hard to conform to.

A Note About The DOCTYPE

Your pages must have a DOCTYPE declaration if you want them to validate as correct XHTML.

Be aware however, that newer browsers (like Internet Explorer 6) might treat your document differently depending on the <!DOCTYPE> declaration. If the browser reads a document with a DOCTYPE, it might treat the document as "correct". Malformed XHTML might fall over and display differently than without a DOCTYPE.

Lower Case Tag And Attribute Names

Since XHTML is case sensitive, and since XHTML only accepts lower case HTML tags and attribute names, a general search and replace function was executed to replace all upper case tags with lowercase tags. The same was done for attribute names. We have always tried to use lower case names in our Web, so the replace function did not produce many real substitutions.

All Attributes Were Quoted

Since the W3C XHTML 1.0 Recommendation states that all attribute values must be quoted, every page in the web was checked to see that attributes values were properly quoted. This was a time-consuming job, and we will surely never again forget to put quotes around our attribute values.

Empty Tags: <hr> , and <img>

Empty tags are not allowed in XHTML. The <hr> and tags should be replaced with <hr /> and .

This produced a problem with Netscape that misinterpreted the tag. We don't know why, but changing it to worked fine. After that discovery, a general search and replace function was executed to swap the tags.

A few other tags (like the <img> tag) were suffering from the same problem as above. We decided not to close the <img> tags with </img>, but with /> at the end of the tag. This was done manually.

The Web Site Was Validated

After that, all pages were validated against the official W3C DTD with this link: XHTML Validator. A few more errors were found and edited manually. The most common error was missing </li> tags in lists.

Should we have used a converting tool? Well, we could have used TIDY.

Dave Raggett's HTML TIDY is a free utility for cleaning up HTML code. It also works great on the hard-to-read markup generated by specialized HTML editors and conversion tools, and it can help you identify where you need to pay further attention on making your pages more accessible to people with disabilities.

The reason why we didn't use Tidy? We knew about XHTML when we started writing this web site. We knew that we had to use lowercase tag names and that we had to quote our attributes. So when the time came (to do the conversion), we simply had to test our pages against the W3C XHTML validator and correct the few mistakes. AND - we have learned a lot about writing "tidy" HTML code.

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W3Schools was converted to XHTML in December 1999