As far as I know it shouldn't be a problem. I've used Javascript before and it's been fine. I had a quick look at your code and don't think that the template editor has altered any tags. The error message 'undefined' seems to point to something else.
Incase your interested the error comes up at line 30:
window.fw_menu_0 = new Menu("root",140,20,"Times New Roman, Times, serif",12,"#6699cc","#ffffff","#006699","#6699cc");
Glenn
Links 2 Mods Site:
http://cgi-resource.co.uk/pages/links2mods.shtml
Incase your interested the error comes up at line 30:
window.fw_menu_0 = new Menu("root",140,20,"Times New Roman, Times, serif",12,"#6699cc","#ffffff","#006699","#6699cc");
Glenn
Links 2 Mods Site:
http://cgi-resource.co.uk/pages/links2mods.shtml