Modify the Document Type Definition (DTD)
Many of the best AJAX apps activate by using custom triggers that do not qualify as valid HTML. I used to think that all was lost, and that there was a mandatory trade between functionality and usability. This is not so: doctype information may be appended to include your triggers.
For instance, I use a modal window system called LightWindow that has “author” and “caption” triggers to relate data to the script when a user clicks on an image. Neither of these triggers will validate under the XHTML 1.0 DTD. Here’s the code to fix it:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
[
<!ATTLIST a author CDATA #IMPLIED>
<!ATTLIST a caption CDATA #IMPLIED>
]>
This is how it breaks down:
<!ATTLIST element attribute dataType #IMPLIED or #REQUIRED>
Since my elements relate to linked files e.g.(<a href=) that I want to open with LightWindow, I use the element ‘a’ for link. The attribute is what you are using to communicate with your app and is also what is causing your document to not validate. The dataType can likely just be left as CDATA as it handles any kind of data. It is also likely best to leave the type defenition as #IMPLIED or optional for these purposes. A more in-depth article can be found at A List Apart.
Fix invalid symbols by changing them to HTML
If you are using a script in your document that is called using symbols such as the ampersand ‘&’ or equals ‘=’ these will cause the validator to choke. Consider using their HTML forms amp; and #61; (with ampersands in front) respectively. A complete list of symbols and HTML translations is available at the Web Design Group’s site.
For example, a line on my site used to look like this:
<link rel=“stylesheet” type=“text/css” href=“combine.php?type=css&files=dlinn.css,lightWindow.css” />
But now looks like this:
Still having problems with CSS?
Yeah, me too. We’ll just have to hang in there until the newer standards (that have existed for years) are adopted or hell freezes over.