Alexa Toolbar

Alexa is a tool that can help measure the success of a website. Like Google Page Rank, you should not accept the results as gospel on how your page is done.

Since Alexa collects traffic data by internet users who have installed the Alexa Toolbar, it is not a scientific measure of the true site traffic ranking, or more popular importatnly industry.

This also means that should not discount the tool. You can use it but also know its limitations. True SEO uses many tools and techniques that are discussed in wholistic manner.