When you try to install add-ons from third party sites from other than AMO, Firefox shows a warning like this :
“Firefox Prevented the site(www.download.com) from asking you to install software ”
To solve this
- Open Firefox, click on menu > Options > Security
- Under General, click on Exceptions for the “Warn me when sites try to install add-ons” option
- Then a windows opens, which lets you enter the web site address from which you want to install add-ons, type that site address, and click “Allow”and click close.
4. Now try to install the add-on by visiting that site it will be installed now without any issues.