It is imperative that any Search Engine Marketer use the following webmaster tools provided by Google, Yahoo! and Bing.
Google Webmaster Tools- Great for all its features except for determining how many backlinks are coming into your site
Yahoo! Site Explorer- Great for all its features and the best tool for determining how many backlinks are coming into your site
Bing Webmaster Central- Great for seeing your position and relevance on Bing
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