Took this guide directly from Raymond.cc, so all thanks go to him/them, I just found it, and though it would oh so fun to share
This article is written and contributed by Utkarsh
We all use file hosts like Rapidshare and Megaupload these days. Most of the data hosted on these file hosts are in various parts. Sometimes, due to illegal activity of the hosted files or due to no download for a long time, these files get automatically deleted from the servers. Thus, it becomes very annoying when you have downloaded most of the files and come to find that one of the file links is either dead or blocked by Rapidshare due to possible illegal contents in the file(s).
That is when link checkers come in handy. Rapidshare provides free link checking facility called Rapidshare Checker at their homepage. It is, therefore, advisable to check the integrity of the links before starting to download files from the file hosts. But, it is cumbersome to check the links every time on their homepage. Today, Iím going to show you a method (for Firefox users only) on how to automatically let Firefox check the integrity of links of various file hosts while you visit the page with download links.
1. Download Greasemonkey add-on and install it in your Firefox.
2. Download Rapidshare Links Checker User Script from here and install the User script using GreaseMonkey.
3. Restart Firefox
Now, whenever you go to a webpage that contains Rapidshare, Megaupload, Filefactory, etc links, this User Script will come into play. If it finds dead links, itíll have an X icon at the end of the link and a checkmark icon for a valid working link.
Here is another script for Greasemonkey called Universal Link Checker which claims to check links for the following websites: rapidshare.de netload.in easy-share.com mediafire.com megashares.com depositfiles.com vip-file.com yourfilehost.com sendspace.com filebase.to link-protector.com bitroad.net vip-file.com filenavi.com uploadbox.com zshare.net letitbit.net
You can install this GreaseMonkey script in the same way as described in Method 1 above. This script is created by the user who created RapidShare Links Checker but it works differently in background.
There are many Firefox add-ons which work in a similar fashion but their working is limited to only Rapidshare. One of such add-on is RSE Tools for Firefox.
Features of RSE Tools:
# Getting Rapidshare links from a specific page
# Testing selected Rapidshare links on a page
# Search Rapidshare files for selected terms using RSE (Rapidshare-Search-Engine)
Here is another Greasemonkey script called AIO Links Checker which work very similarly as Rapidshare Links Checker because it is based on it except it is claimed to be smaller and faster by the author.
Method 1 as Method 2 sometimes doesnít work at many occasions and it impacts your Internet bandwidth to some extent. So, Iíd recommend Method 1.