You may want to check with your bank on whether it's web site is compatible with Firefox 4.

If it is supposed to be compatible, did this site work in the past, or is this a new issue? If it worked in the past, did it always work consistently with Firefox 3.6 and only stopped working in Firefox 4?

I'm not sure but it seems that the bank's website might not be compatible with Firefox 4.0. Last time I did online banking with this particular account was the beginning of May. My other bank accounts are still accessible (I'm keeping my fingers crossed on that one). I was told to disable cookies and clear cache by a Firefox support volunteer. I was also told to enable cookies from the bank's website by the bank's online banking support person. I did both, and neither worked. Please help!! Thank you .

Actually, you wouldn't want to disable cookies, just clear the ones you had saved from previous visits to the bank's site.

Firefox 4 is a little stricter about HTML than Firefox 3 was. To see whether that is related, you could try turning off the new HTML5 parser in Firefox 4. Please save any unfinished work first.

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the filter box, type or paste html5 and pause while the list is filtered

(3) Double-click html5.parser.enable to toggle it to false (it should turn bold).

Then return to the bank page and reload. Does that make any difference?

Did not work. Can't use other browsers, either (chrome, explorer, safari)...

Oh, if a site won't work in any browser, it could be that your security software is blocking some information the site requires. For example, your bank requires cookies and it might requires referring site information. If you have a product like Norton Internet Security, check its privacy settings and allow all information to go through to the bank.

Also, just in case your computer is infected by malware, you may want to run some supplemental scans. These two tools are highly regarded:

Malwarebytes Anti-malware : http://www.malwarebytes.org/products/malwarebytes_free

SUPERAntiSpyware : http://www.superantispyware.com/

Thank you! I forgot to mention that I did have a problem with rogue security virus last week (Vista Internet Security 2012 or something of that sort). I downloaded spybot to get rid of it. I also use CA security software for antivirus. Could it be that either spybot or CA are blocking something? I am not that computer savvy to fix this issue, I'm afraid...

Rogue software can break lots of things. You might want to try a forum that specializes in fixing security problems. I have seen this one recommended several times:

http://www.geekstogo.com/forum/

Thanks for all your help and recommendations again! I changes my cookie setting in CA internet security and it works now!