Craigslist is not the only classified ads site on the web but it certainly is the most popular - ranking ninth most popular in the US.
There are no fancy graphics on Craigslist's homepage
But if you think Craigslist is some flashy, whizbang 21st Century website you would be wrong: the opening page consists of row after row of blue underlined hyperlinks - no other colour or graphic in sight.
This text-heavy, very basic website is used by more than 15 million people each month in 450 cities and the idea of a better designed website entering the market, offering the same service, does not appear to threaten Craigslist CEO Jim Buckmaster.
"Certainly there are well capitalised companies doing things that are similar but our very modest approach works for end users," he explained.
"For an individual user their ad can be as flashy as they like but the top level pages load faster if they're simple, blind people are able to access our site, it doesn't get in people's way.
And to add to the peculiarity of Craigslist, instead of cashing in on its popularity, the creators have chosen not to have any ads - no banners, no click-throughs - nothing. Their only source of income is charging companies and people in certain cities for certain types of ads.
"The reality is that our users haven't asked us to run text ads so despite the fact we're told it would raise us millions per month, it's not something we're looking at," Mr Buckmaster said.
Craigslist got started in 1995 when former IBM systems engineer Craig Newmark created an electronic mailing list for like-minded friends in the San Francisco Bay area. The company now consists of just 23 people working out of a Victorian house in San Francisco's Inner Sunset neighbourhood.
Traditionally the web has been great for getting something from half way across the globe. Craigslist has capitalised from helping people finding something from their own locality.
Adverts online have their advantages: their life spans can be indefinite, they are searchable and you can get an immediate response. Their main competitors are newspapers.
"I think that the demise of newspapers has been overstated," said Mr Buckmaster. "Ninety percent of the revenue is still in print."
"Online classifieds, like Craigslist offered for free often reach a different group of people with different goals in mind, people who probably never would have posted in print classified because the expense was prohibitive.
"If you lower the price to free and make it ubiquitously accessible, people start using the medium of classified ads for all kinds of things that haven't been seen before."
Before many other user-generated sites took steps to prevent people misusing their businesses, Craigslist put in place a flagging system.
"I don't think 23 people or even hundreds or thousands can effectively police a site of this size getting over 15 million classified ads each month of unlimited length," he said.
"So what we've done is put flagging links on each posting where users if they see something out of line or inappropriate can flag the ad and if enough users agree and also flag the ad it comes down automatically without us even seeing it."