What's worse is that a lot of that advertising may never come back to newspapers even if the real estate sector recovers. That's because a significant chunk of those advertising dollars are moving - you guessed, online.

Exactly how much of a shift is occurring is difficult to measure in terms of dollars or market share, but several real estate executives say they are making a conscious decision to move money out of newspapers and onto the Internet as that medium grows in importance as a tool for researching home-buying decisions.

Granted, a significant amount of the declines in real estate advertising in newspapers can be attributed to the general weakness in real estate markets, particularly in hard-hit markets such as California and Florida, which were booming a year ago - leading to big gains in advertising back then.

This week Tribune Co., the No. 2 publisher by circulation, posted a 24 percent drop in the second quarter, while industry leader Gannett Co. has reported a 9.9 percent decline and McClatchy Co. reported a 19 percent decline, citing big losses in California and Florida.

Like the housing market itself, much of the up-and-down movement in newspaper real estate advertising can be viewed as cyclical, meaning it will be weak in down markets and bounce back in the upward part of the cycle, whenever that comes up.

But what's worrying analysts this time around is that real estate could become the next category of classified advertising - after help-wanted ads - to mark a significant and permanent shift away onto the Internet. The stakes are big for newspapers since classifieds are highly lucrative and make up more than 35 percent of their revenues.

Mike Simonton, the top media industry analyst at the Fitch Ratings credit analysis service, says that currently a good 30 percent of help-wanted classified advertising is now online, while the Internet's share of real estate and auto classified advertising is lower, at about 15 to 20 percent, but poised to move higher.

"The threats from the Internet are real," Simonton said. "Newspaper advertising should remain under pressure until newspapers are better able to address the threat of online advertising."

Representatives of several major real estate franchisors said in interviews that many home sellers still see newspaper advertising as an essential component of selling a home, but that younger brokers, home sellers and buyers are clearly more focused on using the Internet.

"For our agents, newspapers are an old standby," said Abby Lee, director of regional advertising in Denver for RE/MAX, a major real estate franchisor. "With younger agents, there's a trend of going online. There's a realization that's where they need to be."

Suzy Antal, director of marketing, communications and public relations for Prudential Real Estate Affiliates, a unit of Prudential Financial Inc., said many Prudential agents have been pulling back on advertising during the current downturn, but as they return, they're shifting ad budgets to their own Web sites, creating blogs, and taking different approaches beyond newspapers.