Yes, and there are lots of ways they can do it. Web pages are a flexible platform for exchanging information, but that also means it can be easy to track what you’re looking at on them. The first method is through third-party content. Say Company A is an advertising or tracking firm. When you visit sites that display A’s ads or use A to track their visitors, A can identify your browser and see what pages you visit on those sites (and more). To learn how to mitigate these tactics, go to ssd.eff.org/cookies. Also, if you click on links to A’s site from other sites, A’s site can tell which page you came from. To circumvent this, copy and paste the URL instead.
Sometimes a link to another Web site actually goes to a page on an advertiser’s site and redirects you to the real destination after recording where you’re going. Place your cursor on the link to see the address, find the URL you want embedded in it, and type it into the browser rather than clicking. Or get privacy-protection software like Privoxy (free; privoxy.org) that warns you if you’re about to click a redirecting link. (Search engines also redirect you, so if you use Google, install the CustomizeGoogle plug-in and enable “Remove Click Tracking.”) Finally, watch out for toolbars that add features to your browser—they may report sites you visit back to the company that produces the toolbar.
Peter Eckersley is a staff technologist with the Electronic Frontier Foundation.