Many site issues can be caused by corrupt cookies or cache. In order to try to fix these problems, the first step is to clear both cookies and the cache. Note: This will temporarily log you out of all sites you're logged in to. To clear cache and cookies do the following:

1. Go to Firefox > History > Clear recent history or (if no Firefox button is shown) go to Tools > Clear recent history.
2. Under "Time range to clear", select "Everything".
3. Now, click the arrow next to Details to toggle the Details list active.
4. From the details list, check Cache and Cookies and uncheck everything else.
5. Now click the Clear now button.

Further information can be found in the Clear your cache, history and other personal information in Firefox article.

Did this fix your problems? Please report back to us!

Thank you iamjayakumars for your reply.

I did what you wrote, but it did not solve the problem. I cleared the cache also separately using Mackeeper, but that did not solve it either.

I am very much looking forward to hear from you again to see how this can be solved. Thank you very much again for your kind support. Silvia

Please update to Firefox 19.0.2 Update Firefox to the latest release then try again

Use these steps to remove saved (form) data from a drop down list:

1. Click the (empty) input field on the web page to open the drop down list
2. Highlight an entry in the drop down list
3. Press the Delete key (on Mac: Shift+Delete) to remove it.

• http://kb.mozillazine.org/Deleting_autocomplete_entries