Are these normal ads in web pages, or additional ads injected into them? If they are extra ads, one of your other extensions might be the culprit.

Try disabling ALL nonessential or unrecognized extensions on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, if in doubt, disable.

Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Does that change the ads you see?

Also, you might previously have been using a list of filters for Adblock Plus that fine-tuned it for various sites. Do you recall installing anything like that?

It sure looks like it. Did what you suggested, and was astonished to see 4 unatuthorized unknown files in it. Disabled all, and went to the latest web site where I was being crowded out .... and all gone!!! What makes me wonder now is how they got in; I have been reformating this week end, and merely installed FF as my browser.....so instenct tells me that somehow FF is involved?????? THANKS!!!!!!!!! Feel great to surf now with pleasure !!!!!!!!!

Note that some installers or updates come with unwanted additions, so make sure to always look for check boxes if you update or install programs like Java and Flash.

You might also want to visit the Windows Control Panel, Uninstall a Program, an click the "Installed on" column heading to bring the most recent additions to the top. Just in case you got any other bundled surprises.