I am editing some code from a previous developer for a timetable filtering system. The way I would tackle this myself is using jQuery so I am having a few issues debugging t
This error occurs when the you don't follow the W3C tag recommendations. IE is very picky about this and Firefox is not. You can read more here: http://blog.rakeshpai.me/2007/02/ies-unknown-runtime-error-when-using.html
Here's a similar question that might help you: Fixing "unknown runtime error" in IE8
Here's another link on the same thing, and specifically the "form within a form" issue: http://jadendreamer.wordpress.com/2009/06/02/internet-explorer-fix-unknown-runtime-error-using-innerhtml-ajax/