Do the screen shots in this thread at bit-tech forums illustrate the symptoms you describe?
If so, then it is probably something like an intellitxt.com script being used on those pages you visit.
If that's the case then a script blocker like NoScript for Firefox should solve the problem.
As for an ad-blocker, Adblock Plus for Firefox works well.
Along with Adblock Plus you might want to look at Adblock Plus Pop- Addon. I haven't tried it so can't comment.
In Opera for Script blockers either one of these two work:
NotScripts my preference, or
Just use one or the other not both.
For ad blocking these work:
Adblock Plus for Opera or
AdBlock for Opera.
One or other, not both.
Can't recommend anything for Internet Explorer or Chrome as I use neither. Hopefully, someone will show up soon that knows what you can use for them.
The only other thing I can suggest for them is, using your favorite search engine(google, DuckDuckGo, etc...) and search for comparable add-ons.