Do you have a custom 404 page at the moment? Many websites on the internet do not have a custom 404 page. They stick with the default one on their server. Set up one and integrates adsense and/or referral links.
I have set one up that includes Google Search, and Firefox referrals. […]

Popularity: 5%

With Firefox and Greasemonkey, you can check the pagerank of domains at TDNAM. This tool is very useful if you are looking to snag a cheap domain with pagerank. It will put a pagrank image under every domain. Look below to see an example.

Requirements:
* TDNAM.com Account ($5.00/year)
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Popularity: 3%