I use Firebug to debug a shrink-wrap Perl/Catalyst application with AJAX/JS bells and whistles. Before Firebug this was extremely difficult, as I am used to my Perl/Java code being corrected in my IDE, and I have no such tool for JS. With Firebug, along with Catalyst/DBIx::Class's debug information, I can monitor my application's execution from the client side code, to the network communications, to the server script execution, to the database queries, and back. This makes my job much, much easier than it would otherwise be. I use EPIC/Eclipse to do Perl. I use Dreamweaver sometimes to do HTML, but I hate it as I end up fighting it three times as long as it takes to write the code by hand, so I end up doing it by hand in a split screen window. What do you guys use? I still don't have a JS IDE that will do syntax checking of any kind. I don't even have syntax highlighting for JS. Is there such a thing for Eclipse?