The legislation -- two similar bills pending in the House and Senate -- would empower the Department of Justice and copyright holders to shut down Web sites that violate intellectual property or sell counterfeit goods. A range of U.S. businesses and their trade groups, including the U.S. Chamber of Commerce, pharmaceutical and media companies and publishers, say it would lead to more jobs and revenues and promote consumer safety.

Opponents, including large and small Internet companies and First Amendment advocates, argue that it would stifle innovation and lead to censorship. Here are key issues to consider:

Q: What are SOPA and PIPA?

A: SOPA, or the Stop Online Piracy Act, is a House bill introduced in October that aims to expand the powers of U.S. attorneys general and copyright holders to crack down on Web sites that display or link to copyrighted intellectual property or counterfeit goods. The U.S. Senate has a similar bill pending, the Protect IP Act, called PIPA.

Any Web site that "engages in, enables or facilitates" copyright infringement could be placed on a list of Web sites that would be blocked by Internet service providers. Copyright holders could also ask the court to force online advertising companies to stop doing business with the allegedly infringing Web site, have payment processors cease financial transactions with the site or get search engines to stop listing such sites.

SOPA opponents also say that many provisions in the bills are vaguely written and that Web sites that display user-generated content are particularly vulnerable.

Q: How likely is it that the bills will pass?

A: The longer they stay in committees, the less likely the bills will pass. SOPA is still being debated...