Google has been tinkering with the design of Gmail lately, which raises the possibility that Firefox may be mismatching old cached files with new ones, or sending the site cookies that correspond to an older design.

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Bypass Firefox's Cache

Use Ctrl+Shift+r to reload the page fresh from the server.

Alternately, you also can clear Firefox's cache completely using:

orange Firefox button (or Tools menu) > Options > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove your google.com cookies (save any pending work first). While viewing a page on the site:

• right-click and choose View Page Info > Security > "View Cookies"
• Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"

That will open a dialog where you can remove the individual cookies.

Then try reloading the page and logging in again. Does that help?

Thanks for your response jscher2000. I completed both steps of your recommendation and unfortunately am experiencing the same problems. Any other suggestions?

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can remove all data stored in Firefox from a specific domain via "Forget About This Site" in the right-click context menu of an history entry (History > Show All History or View > Sidebar > History) or via the about:permissions page.

Using "Forget About This Site" will remove all data stored in Firefox from that domain like bookmarks, cookies, passwords, cache, history, and exceptions, so be cautious and if you have a password or other data from that domain that you do not want to lose then make a note of those passwords and bookmarks.

You can't recover from this 'forget' unless you have a backup of the affected files.

It doesn't have any lasting effect, so if you revisit such a 'forgotten' website then data from that website will be saved once again.

Thanks cor-el! I tried the safe mode and gmail was flawless. Then I re-opened Firefox and selected the reset. Oops. I misread your message. I had to reset Gmail as a homepage for my email button. Other than that, all seems well. The Gmail is still working. I can now open old emails and attachments and the compose new email no longer opens a blank browser window.