Coors.com, animation site Mondo Mini Shows and AmericanGreetings.com were the fastest growing sites on the Web last week, as the trio benefited from people passing along their gags and cards.

For the week ended Oct. 30, Coors.com got the highest boost at 285 percent over the previous week. The beer company's interactive Halloween game with a frosty glass helped drive traffic nearly fourfold to 2.2 million, Nielsen/NetRatings said.

Visitors flocked to No. 2 Mondo Mini to see its Halloween-themed interactive animated short, boosting traffic 208 percent to 2.3 million. AmericanGreetings.com, which offers electronic greeting cards that are easily sent and passed along among people celebrating Halloween or other holidays, got a 154 percent jump in traffic to 9.7 million.

Online consumers passing along a company-supplied game or gag to family, friends and colleagues is called viral marketing, a very effective email advertising scheme.

"The data shows us that an email viral-marketing campaign does not have to be product-focused to be successful; it simply has to generate 'buzz,'" Gerry Davidson, Nielsen/NetRatings media analyst, said in a statement.

Another site that saw increased audience traffic due to viral marketing emails was Shortu

l.com, which saw a 60 percent boost in the number of unique visitors to 8.1 million. The Shorturl.com spoof invited visitors to look up their driver's licenses online, complete with picture and personal information. Visitors instead got bogus licenses showing the face of an ape.

People 45 years old and older made up more than 60 percent of the visitors to the sites with interactive games, accounting for 62 percent of Coors traffic and 65 percent of Mondo Mini Shows traffic. Women of all ages were the primary visitors to AmericanGreetings.com, accounting for 65 percent of traffic.