You are currently using Firefox 25.0 - Aurora

Please try using Firefox 23.0 and do a clean reinstall.

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Please report back to see if this helped you!

Thank you.

Hello,

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• You can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

Also check for malware, with all the below programs.

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

When I open the about:about page I don't see an entry for about:tab. Something new? Something related to an add-on??

sorry, I miss-spelled, it's about:newtab ofc

You should still try safe mode, it may be a addon affecting it.

What is the name of the file you have many copies of in the downloads library?

it is a .pdf file, which is book about mathematics

Weird. What is the exact name of the file? Example: geometryclass.pdf

Also go to your downloads library, right click one of the pdf files and select "Copy Download Link". Then right-click > Paste the link here.

It sounds like your about:newtab url was set to this pdf link. Which would cause it to download the file everytime you went to the about:newtab page.

We need to reset this setting.

Copy and paste this into the url bar and press enter:

• about:config?filter=browser.newtab.url
• Click the "I'll be careful, I promise!" button

Then right-click browser.newtab.url and choose Reset. Now close and reopen Firefox. Is the problem gone?

I tried, reseting the browser.newtab.url setting, but did not help. After all, clean reinstal solved the problem. I would really like to know, how to set custom things to about:newtab though.. thanks anyway guys

The about:config method should work for about:newtab, but extensions can override it (and a user.js file can revert it at the next startup).

(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 search box above the list, type or paste newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter your preferred page:

(i) Page thumbnails (default) => about:newtab

(ii) Blank tab => about:blank

(iii) Built-in Firefox home page => about:home

(iv) Any other page => full URL to the page

Press Ctrl+t to open a new tab and verify that it worked. Fixed?