Looks fine here if I zoom the page via a few times Ctrl + + and then refresh the page via F5.

Can you attach a screenshot?

• http://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

Use a compressed image type like PNG or JPG to save the screenshot.

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

http://dl.dropbox.com/u/28403943/mozilla/one.png http://dl.dropbox.com/u/28403943/mozilla/three.png http://dl.dropbox.com/u/28403943/mozilla/two.png

OK, I can replicate this after looking at your screenshot. I hadn't tried to zoom out the page to make it smaller, but with zooming out and I also get a smaller view port with scroll bars after a refresh with F5. On older Firefox versions I see two instances of that page after a refresh. A new zoomed version appears in the top left and the old zoomed instance stays visible at the same position. So this looks like a bug to me in Firefox 18+. Firefox 17 (including the current 17.0.3 ESR) seems to work OK apart from the doubled web page that is corrected after a second refresh.

how can i ask developers of mozilla to fix this bug?

You can file a bug report on Bugzilla: http://bugzilla.mozilla.org/