The Microsoft Internet Explorer browser can automatically detect these ratings and block out sites likely to offend. But many of the free-speech advocates who denounced the CDA and advocated filtering as a better alternative are now worried. As with any Internet debate, there's a good deal of nonsense afoot. Some filtering critics argue that Web site designers will post only the most inoffensive materials to avoid being blocked - a sort of de facto censorship. Most people will choose bland fare, but that happens with any medium that caters to the public.
Filters just make it easier to avoid the seamier stuff.
There are, though, more reasonable concerns. For instance, many Web site builders edit their sites to avoid being blocked by filtering software if they know there's a problem. If they get blocked anyway, they may never know it because the blocking software companies have stopped notifying sites that they are being blocked. Dick Gorgens, chief executive of Microsystems Inc. in Framingham, said Microsystems used to send e-mail to sites that were being blocked by the company's Cyber Patrol product but decided it was too much trouble. This won't do.