A legal fight may be brewing over Web browser add-ons that let people avoid advertisements. These add-ons are growing in functionality and popularity, which has led legal experts surveyed this week by CNET News.com to speculate about when the first lawsuit will be filed. If ad-blockers become so common that they slice away at publishers' revenues, "I absolutely would expect to see litigation in this area," said John Palfrey, executive director of Harvard Law School's Berkman Center for Internet and Society. Firefox's Adblock plug-in is probably the most prominent way to configure Web browsers not to display advertisements. It lets people block ads from individual Web sites such as Doubleclick.net or through configurable directories, like "/banner". Similar plug-ins are available for Opera, Safari and Microsoft's Internet Explorer.