Here is a picture.

Is it just one site, several sites, everywhere?

Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache

Press the <Alt> or <F10> key to bring up the tool bar. Then; Tools > Options > Advanced > Network > Cached Web Content: Clear Now On Mac it is Firefox ->Preferences-> Advanced ->General and

• Remove Cookies

Press the <Alt> or <F10> key to bring up the tool bar. Then Tools > Options > Privacy. On Mac it is Firefox ->Preferences-> Advanced ->General Under History, select Firefox will Use Custom Settings. There is a button on the right side called Show Cookies.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode; Press the <Alt> or <F10> key to bring up the tool bar.. Then Tools > Options > Advanced > General. On Mac it is Firefox ->Preferences-> Advanced ->General Look for and turn off Use Hardware Acceleration.

Poke around safe web sites and see if there is still a problem. Then restart.

In case you want to us it;

Forum; Adblock Plus Homepage {web link}

Thank you! I tried again after your reply, this time deleting all cookies, not only those related to the sites I was visiting, and the problem went away. Before that it was a generalized problem, not limited to a particular site, but turning off adblock for a given page allowed it to be displayed properly. Turning it off completely - with my other add-ons enabled - and of course safe mode also had the same effect.

Spoke too soon... In fact, I had left adblock disabled on a few pages. Once I activate it there, the pages are not shown correctly. Other pages are also affected. I cleared all cookies and the web cache to no avail. I had to turn adblock off on the Mozilla Support page in order to post this.

I will try the adblock forum. Thanks again.

This seems to have been caused by Adblock Plus filter list EasyList Italy+EasyList. I updated the list and the problem went away.