The Alexa Toolbar, an application prouced by Alexa Internet, is a Browser Helper Object for Internet Explorer on Microsoft Windows that is used by Alexa to measure website statistics. It includes a popup blocker, a search engine entry box, a link to Amazon.com, a link to Alexa, information about the current Alexa ranking of the website that the user is visiting, and links relevant to the site the user is browsing. By early 2005 there had been over 10 million downloads of the toolbar, according to Alexa. But the company does not provide info on how many of them are actually used. According to one estimate made in March 2003, Alexa had a sample size of 180,000.