Two days ago two of the forum I use stopped working as they did. Google Chrome can open these sites without problem. I have checked that Javascript is working. What can I do to get the sites back to the way they were?

Question

Two days ago two forums I regularly use stopped working properly. One of them is www.mobileread.com, and the main problem is with marking the forums read. The staff there suggested that I check that Javascript is enabled. It is, but the problem remains.
The other site just looks as though there is no styling on the index page; it just shows a list of links.
I can use both sites with Google Chrome just as I did before, so it has to be a problem with Firefox.
There are many other sites I visit, and I have not had the same problem there.

Answer 1

For the one with a styling problem, see what you have for View > Page Style
the normal style is default and "No Style" would wipe out styling but in this area it would apply to all pages.
I don't know of an extension that would selectively turn page styling or off, but look at your extensions.
Both problems could be caused by filters added to "Adblock Plus" extension.
Bring up "Open blockable items [Ctrl+Shift+V]" in ADP by right-clicking on the toolbar/addons bar icon or in the add-on's options. See what is being blocked and the filter that is blocking it. You can easily test filters there and turn them on/off and retest. You can see the filter that is blocking an item, you can use the mouse to see where that filter came from. Choices of what columns to display can be made with the little icon to the right of the column headings in the list.
Attached is a picture of blockable items I see for the www.mobileread.com page. To view a page that you need to view or use, you can try modifying your filters or toggling the "State" column (preferred). You can disable Adblock Plus from the extensions options but that defeats the protection it offers.
If seems that the problem would be an extension, or a style, or theme.