Firefox Text Bold

[iKettles]

Earlier today certain bits of text in Firefox seem to have just suddenly become bold. This means I can't disinguish read emails from unread emails in Gmail. Anyone else had this issue? How can I fix it?

 

[Zefan]

You've probably accidentally held ctrl while scrolling, press ctrl down and scroll to your default font size.

 

[iKettles]

Thought that was the issue as well but still no luck