Please look at this sreenshot...

I am sorry, but I don't see a problem with what the image is showing.

Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences<Enter> in the address bar

Select Advanced > General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

This issue can be caused by an extension that isn't working properly.

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

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

Is it not visible at the top of the Wikipedia tab .. the tooltip of the tab `sizeof- Wikipedia .....' is around twice longer and thrice broader than expected

I will try to see if disabling Hardware acceleration solves the issue.. thanks for your replies

This is more likely caused by an extension or theme than by hardware acceleration, so make sure to check for issues cause by add-ons.

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