Centre column of 3 col layout problem - Works in IE but not firefox!?

My site has three columns.

left-middle-right

The middle column in IE is right underneath the header as it should be.
On firefox the middle coumn is as far below the header as the height of the right column.

I have tried everything but i cant get it to look right in both browsers.
It is all done with floated divs and doesn't use any tables at all.

Please can someone help me!

www.datahq-online.co.uk

Thank you!

Most of the validation errors are to do with the URL's that the CMS i use creates and to do with a bit off ajax i popped in.

None of which are going to cause my problem.

I fixed the recurring ID i had but it has not made any difference.

Thanks for the suggestion though.

It still has that problem.

I have put my CSS file through a stand alone validator and apart from some colour things and where i have specified a height twice it is fine.

Can anyone help me!

I am designing for firefox but i cannot get it to work properly in firefox.

I just happened to look at IE and noticed it all looked fine to bo honest.

The centre being low and the menu dropping is what i am trying to fix!

Thanks for your suggestions, keep them coming!

I have posted this problem on three different forums and have had the same answer on them all which was VALIDATE YOUR CSS AND HTML.

Now i think validating is all well and good but it is not the be all and end all. Look at some of googles sites (search engine results page for example) they dont validate! I know that it is one thing to tick off the list of things that could be the problem but seriously!

Anyway, someone on sitepoint.com saw that i had put a div on it's own with clear:both style which was pushing the content down.

All i had to do was put it in it's containing div and take the clear:all out (as it's containing div was doing the positional work)

The naughty div was "infobottom".
It is now fixed and the site looks fine on both IE and firefox.

Thank goodness for that!

Thank you for your time though, it does not matter what you say so much, it is the time you have spent to help me that counts and i am very very grateful indeed.

Maybe not, but are their invalid bits small issues, like "no alt attribute found"? Because while I agree that you can feasibly ignore some invalid warnings, such as the aformentioned "missing alt attribute", and even "font elements aren't supported anymore", there are MANY others you can't ignore.

Unclosed elements, improperly nested elements, etc. Those ALWAYS NEED to be corrected when trying to figure out cross-browser issues.

Thanks for thanking us, you're very welcome.