Before Firefox 13 release, to save a link on a page in Firefox all user need to do is hold the Alt button on keyboard and left click on that link, this can also be done by right-clicking on the link and selecting “Save link as “ option from the context menu, but former one is more convenient and faster way to download links, alt+click to save links behavior has been disabled in recently released Firefox 13 reason being accidental Alt+clicks saving links can be annoying for users and Mozilla thought this shouldn’t be the default behavior, however Mozilla added a hidden preference in about:config to revert to that behavior, here is how to re-enable Alt+click to save links in Firefox.
Make Firefox to save links when Alt+click combination is used
1.Open Firefox address bar and type about:config and press enter
2. Now find the preference “browser.altClickSave” and double click on it to turn its value to “True”.
3. Restart the browser, from now onwards if you press Alt+Click links will be saved.