What are web workers?
What are limitations when serving XHTML pages?
Perhaps the biggest issue is the poor browser support XHTML currently enjoys. Internet Explorer and a number of other user agents cannot parse XHTML as XML. Thus, it is not the extensible language it was promised to be.
What are pseudo classes in CSS and what are they used for?
Pseudo classes are similar to classes, but are not explicitly defined in the markup, and are used to add additional effects to selected HTML elements such as link colors, hover actions, etc.