Alexa can only collate data from surfers who also have the Alexa toolbar installed.
They believe that 2% (roughly) of internet users have the Alexa toolbar.
So if two people click to your site, and they both have the Alexa toolbar, then they calculate that you have actually had 100 visitors.
They also don't understand unique visitors, so if one person with the Alexa toolbar visits your site 10 times a day then they put it down as 1000 visits!
Furthermore (hope you're keeping up with all this

) , they don't differentiate users, so..........If you have the Alexa toolbar installed, and you visit your own site 200 times per day, then Alexa will think that your site gets 10,000 visits each day!
The reason I found this out is because I have the Alexa toolbar, and when I was building my last site I was clicking on different pages hundreds of times each day for about 4 weeks.
After which I received an email from Alexa saying 'congratulations, your site is now one of the top 100,000 sites on the internet.........'
The site was 6 weeks old and hadn't even been spidered.
:shock:
Alexa and a pinch of salt are good things to take together.
:wink:
JB