But their experiments might go awry by turning customers away, experts say. The sites employ a variety of tactics, including ads that a visitor must close before accessing a site's content.
Some sites contain code that disables a browser's Back button.
When the latter step is taken, pages often reload when consumers click on the Back button, either as an intentional lock-in or as a side effect of animation technology, such as Macromedia Flash. These efforts are driven by the sagging results of online advertising campaigns. To combat these troubling trends, sites need to pump up their usage metrics and accept increasingly challenging performance demands from advertisers, experts say. The firm has tracked 35 sites using lock-ins but acknowledges there are more. Lock-ins were previously used mostly by pornographic and gambling sites.