(Editor's Note: A blog post from Zillow.com -- the original source for this story -- did not accurately report the numbers from comScore. Go here to see more on the snafu, but Zillow still trails Realtor.com in terms of unique visitors).

Zillow.com has been on a bit of a roll in the past few days. Earlier this week, the Seattle company announced a new initiative to offer rental listings through its Web site. Now, word comes that the company has become the most visited real estate Web site in the country for the month of November, just surpassing Realtor.com.

According to comScore numbers, Zillow attracted 5,231,000 visitors during the past month. That compares to 5,223,000 for Realtor.com.

What's even more impressive is that Zillow -- backed with $87 million in venture financing -- achieved that milestone in less than four years.

Of course, Zillow now must maintain that position and grow its lead over its rivals. The money-losing company also needs to drive revenue and profits, something that Rich Barton and crew are becoming more focused on.

Zillow actually says its internal numbers show a much higher number of unique visitors, running at an average of about 8.3 million visitors for the month. And the comScore results come out a few days after Experian Hitwise ranked Zillow as the second-largest online real estate site behind Realtor.com.

John Cook is co-founder of TechFlash. Follow on Twitter @johnhcook.