Forum Moderators: not2easy
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About your problem...
Yes, in firefox the vacancies page jumps - on hover of the table, it forces in empty cells (it's your javascript - it's not doing it very well)
By the looks of things, you have a lot of work to do...
And your problem doesn't look like an easy answer, rather your method of coding needs a lot of relearning.
A couple of tips: don't develop it to work in IE first - not if you want it to work in all the other browsers. If you're happy for it just to work in IE, then go for your life, but otherwise, develop and test first in a standards-compliant browser. That way, you know that if something's not displaying correctly in IE, it's mostly always IE's fault, and you have a much easier time of fixing it just for IE. Also, when you get it to work in one standards-compliant browser, you've pretty much solved it to work in all the standards-compliant browsers. That's what standards are all about :)
If I was you, I would go get Firefox right now if I hadn't gotten it already, and start changing all my code until it worked perfectly in Firefox. Firefox has a good javascript erroring log, and there are several extensions that can help with the debugging process (HTML Validators, etc)
Once I had it working in Firefox, I'd have a quick look in the other standards-compliant browsers just to check (Opera, Opera Mac, Safari, Firefox Mac [though that should never be a problem :D], Camino)
And only then... IE. And then lynx, and an aural narrator, just to tie things off.