In your screen shot, it seem to affect the "bold" face only. This could indicate a problem with a font on your computer, or Firefox might be substituting inappropriately.

You could test that theory by turning off the bolding on a phrase in the page using the Inspector. Right-click the bottom phrase (non-link part) and choose Inspect Element (Q). In the Inspector, on the right side, will be style rules. Uncheck the box in front of font-weight: bold and see whether the text shows normally. (See screen shot.)

Or... could it be some kind of prank? The letters seem to be shifted two to the right in the alphabet. For example, in the button at the upper right:

Log In => Nqi Kp

That seems a bit suspicious to me.

Yes, i checked with inspect element, the issue is for BOLD texts only. So what do you suggest ? to solve this issue ?

As a test, could you inject some style changes into this page (i.e., a non-Facebook) page.

After displaying the page, open the Web Console and paste the following line of script next to the caret (">>") and press Enter to run it:

var r='p{font-family:"Lucida Grande","Times New Roman" !important; font-weight:bold !important;}'; var s=document.createElement('style'); s.type='text/css'; s.appendChild(document.createTextNode(r)); document.body.appendChild(s);

What happens to the posts? If you get gibberish, then there appears to be a problem with Lucida Grande Bold on your system. (This font isn't included with Windows, so I'm not sure how you would get it on your system.)

If Firefox displays Times New Roman, then apparently it isn't finding Lucida Grande on your system. In that case, try this script:

var r='p{font-family:Tahoma,"Times New Roman" !important; font-weight:bold !important;}'; var s=document.createElement('style'); s.type='text/css'; s.appendChild(document.createTextNode(r)); document.body.appendChild(s);

What happens to the posts? If you get gibberish, then there appears to be a problem with Tahoma Bold on your system.

If neither of the above tests show gibberish, either it's something special about Facebook or I need to look at what other fonts Facebook uses.

I did the test, and i got gibberish text, so its the font which is causing the issue. So i need to reinstall the font ?

Note that you can add extra style rules yourself to change the font-family used for the selected element.
Just click within a rule set and start typing.
A colon separates the property name and the property value (the strike though will disappear once you finish the new rule).

You can do a font test to see if you can identify corrupted font(s).

• http://browserspy.dk/fonts-flash.php?detail=1

You can try different default fonts and temporarily disable website fonts to test the selected default font.

• Tools > Options > Content : Fonts & Colors > Advanced
• [ ] "Allow pages to choose their own fonts, instead of my selections above"

Which font has the problem - Lucida Grande or Tahoma?

Since Tahoma is included with Windows, there's probably an internal way to restore the original file.

Not sure about Lucida Grande...

Some Microsoft articles on font settings and clean-up:

• http://windows.microsoft.com/en-US/windows7/Change-your-font-settings ("To restore the default font settings")
• http://windows.microsoft.com/en-us/windows7/Install-or-delete-fonts