Are you receiving an annoying “This download has been blocked by your Security Zone Policy” error? According to a quote from FirefoxFacts:

Starting in Firefox 3, downloads of executable files (e.g., .exe or .msi) may fail and the Firefox Downloads window will contain this message, under the filename: This download has been blocked by your Security Zone Policy.

This issue occurs because Firefox 3 now honors your Windows security settings for downloading applications and other potentially unsafe files from the Internet.

How to fix that?

To change the setting, open Internet Options (via Control Panel or from Internet Explorer -> Tools) and click the Security tab. With the Internet zone icon highlighted, click the Custom level… button. A list of security settings for the Internet zone will appear. Find the “Launching applications and unsafe files” setting (under Miscellaneous) and select “Prompt (recommended)”.

More fixing tips.