dean.edwards.name/moz-behaviors/overview/

moz-behaviors.xml is an XBL binding that allows Mozilla browsers (Netscape, Mozilla, Firefox etc) to use Microsoft DHTML Behaviors with little or no conversion. Mozilla and Explorer may then reference the same DHTML Behaviors (.htc files).

moz-behaviors.xml is the only file you need to enable DHTML Behaviors for Mozilla browsers.

the XBL binding includes code that implements the addBehavior method for Mozilla’s HTML Elements. The code has been compressed using the javascript packer available from this site.

you do not need to write any additional code to implement DHTML Behaviors for Mozilla.

further, when writing behaviors, you do not need to do any browser sniffing. Mozilla’s object interfaces have been extended to enable browser compatibility.

you can view a working example here:
/my/examples/moz-behaviors/

you can download the wrapper and the example here:
/download/