Google could be earning some $497 million a year from the registered owners of website addresses that mimic typographical errors in existing sites, according to a new study.

Harvard University researchers Tyler Moore and Benjamin Edelman estimate that Google could be making millions from the practice, known as "typosquatting," because its network of display ads -- from which it receives a cut of the profits -- run on the typo'd sites.

If it's a frequently misspelled site address -- for example, zddnet.com instead of yours truly --the tactic could pay off handsomely.

Moore and Edelman used a list of common spelling mistakes to generate another list of possible typo domains for the 3,264 most popular ".com" websites, as determined by Alexa.com rankings.

With help from software, the researchers crawled 285,000 of some 900,000 "misspelled" sites to estimate what revenue the domains are generating.

Scale those results, and you're looking at some serious coin:

Expanding to the top 100,000 sites, retaining the 0.7% estimated ratio of typosquatting site, we estimate that typo domains collectively receive at least 68.2 million daily visitors. If these typo domains were treated as a single website, that site would be ranked by Alexa as the 10th most popular website in the world. It would be more popular, in unique daily visitors, than twitter.com, myspace.com, or amazon.com!

The researchers estimate that almost 60 percent of these sites have ads supplied by Google. With some back-of-the-envelope math, that amounts to $497 million per year in revenue.

It's Google's policy to remove ads from these "misspelled" domains if the owner of the original site complains.

Edelman is currently co-counsel on a lawsuit by a firm seeking damages from Google after the tech giant's ads appeared on a misspelled domain targeting the firm's website. He says the lawsuit did not influence the study's results.

Their findings were presented last month at the Financial Cryptography and Data Security conference in Tenerife, Spain.