It could be an add-on incompatibility, but when you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

1. Clear Firefox's Cache

orange Firefox button or Tools menu > Options > Advanced

On the Network mini-tab > Offline Storage : "Clear Now"

2. If needed, delete the site's cookies here

While viewing a page on the site, right-click and choose View Page Info > Security > "View Cookies"

Then try reloading the page. Does that help?

Thank you for the reply and I am sorry it has taken so long to get back to you. I have read other articles about this problem and most people seem to be having trouble with yahoo doing this. You replied in some of those also. However, in one of the articles, another person left a link that says that this problem is a virus mainly affecting yahoo and facebook. They are working ok. It said how to get rid of it on internet explorer, but not firefox and was hard for me to understand. Avast or Spy Bot have not found it and if it is a virus, how do I get rid of it?

Hi Darrell4345, you probably got notified about the additional suggestion in this thread: https://support.mozilla.org/en-US/questions/928967 Did that make any difference?

The word "virus" sometimes is applied to bad add-ons, and in the case of Firefox, you might want to review your add-ons and disable everything that is not essential. You can do that here:

orange Firefox button or classic Tools menu > Add-ons

Check both the Extensions category and the Plugins category. Then restart Firefox. Any changes?