Most serious developers use Firefox, although there is some evidence that Chrome is catching up. I don’t know of any serious developer who uses IE except for testing purposes after making sure the site renders properly elsewhere.
On the whole, the layout in Firefox is the correct layout according to w3c standards. If you are finding differences between the layouts of various standards compliant browsers then the problem is probably because your code is not standards compliant.
Your HTML declares the standard that it will adhere to in its <!DOCTYPE... declaration. If the code that follows does not, in fact, adhere to the declared standard, you have broken your contract as it were with the browser’s layout engine. Once this happens, all bets are off and each layout engine will try to guess what you mean rather than simply laying out your page in the way dictated by the standard. Every layout engine will guess differently.
So the first thing you need to do is to validate your code by submitting your pages to the w3c validator. The easiest way to do this is by installing the Web Developer Toolbar in FireFox and using the facilty located there. When you have the results of the validation you can correct your code (bit-by-bit) and resubmit your pages until you get it right. Some errors are more important than others. Experience will tell you which these are.
Whatever the results, you need to ensure your pages render correctly in all popular browsers (so Chrome, FF, various version of IE (they all render differently), Safari and possibly Opera). It’s usually only IE that causes any serious problems and you can very often get around those by providing separate style sheets for the various versions of IE. You use conditional comments to include the appropriate IE style sheet(s).
HTH
PAE
