Lately a lot of my clients have been asking me to set up appointments for homes they’ve seen online. Unfortunately, those viewings never happened because, in spite of their supposedly current listings, the properties had already been sold. One had been off the market for several months.

I know a lot of you are looking form information online about a prospective home: a record nine out of 10 house hunters searched online last year, according to the National Association of Realtors.

But there are plenty of problems with non-MLS listings, including errors, out-of-date information and properties that are listed on the Web but aren’t actually for sale.

The most common problems are simply errors—listings that advertise gas heating when in fact the house runs on electric heat, or a price cut that hasn’t been updated online. But in some cases, “mistakes” may be intentionally misleading.

These discrepancies often appear on the listings that are posted on the Multiple Listing Service, an online database that listing agents like myself are expected to keep current.

It’s estimated that around 21% of the data agents individually submit for posting on real-estate websites isn’t updated when changes are made to the price or when the property is sold, according to a report released last month by listings website Trulia.com.

For example, some real-estate agents keep listings on their personal websites long after they’ve sold; when home buyers contact the agent inquiring about the property, they’re instead pitched new properties that might not meet their criteria.

Such lagging information is more common with smaller firms’ websites and could be a function of real-estate agents simply forgetting to update those listings.

Either way, for buyers and me, it’s a waste of time.  Popular real-estate listing sites say they try to update information often, but many sites rely on a feed from the MLS, which means it’s largely the responsibility of individual real estate agents to update listings.

Bottom line, when you hire me to find you a new home, I’ll work diligently within the parameters you give me, so you can spend your time relaxing – leave the locating to me.