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 and downloading again. (If the site requires a login, you probably will need to log in again.) Does that help? --- If that doesn't help, can you describe what you are trying to download in more detail? For example, is it a PDF, an image, a video, etc. Does the server usually push it to you directly (e.g., you get the dialog to open/save/cancel), or show it in a plugin, or do you use a downloader to save it?