HTC is a Microsoft propietary file extension that contains a XML file featuring JavaScript actions that can make dynamic web pages when certain events take place. HTC files are included in CSS style sheet this way for example: <span style="behavior:url(sample.htc)">Hello World</span> In sample.htc a XML file would contain some JavaScript actions for each event. These file extensions are non-standard and therefore are not recomendded for developing cross-compatible websites. Firefox has tried to be compatible with HTC, but some steps are still required to guarantee full compatibility. Anyway, if you still want to use HTC and not Javascript, jQuery or qooxdoo, here I give you some websites to learn more about HTC. [http://en.wikipedia.org/wiki/HTML_Components Wikipedia article] [http://msdn.microsoft.com/en-us/library/ms531018.aspx Microsoft HTC Reference] [http://codebetter.com/darrellnorton/2004/12/10/cross-browser-dhtml-behaviors-htc-files/ CodeBetter CrossBrowser DHTML behaviors ]

Why do you need an .htc file? In modern browsers, you should not need it.