William C. Thompson Jr., the former city comptroller who lost the mayor’s race by a smaller-than-anticipated margin to Mayor Michael R. Bloomberg in 2009, asked voters to hit the refresh button Thursday by unveiling a Web site for his 2013 mayoral campaign.

On the site, Mr. Thompson, who is now chief administrative officer of Siebert, Brandford, Shank and Company, a public finance firm, wrote that he hoped to come up with “compelling and innovative approaches to our most pressing concerns: jobs, education, public safety, affordability, transportation and more.”

He also reflected on his loss in 2009 — but only briefly. “The 2009 race is in the past,” he wrote. “I’m running because I care about the future of this city.”

Mr. Thompson’s Web site still has some bugs. For one stretch of the afternoon, visitors to the site got an error message, accompanied, incongruously, by the Chinese character for Zen Buddhism.

So naturally, City Room wondered: what kind of Web presence do the other likely mayoral candidates now have, a good year and a half before primary voters go to the polls?

Two probable candidates, Scott M. Stringer, the Manhattan borough president, and Bill de Blasio, the public advocate, have set up campaign sites that do not declare their mayoral intentions outright.

Christine C. Quinn, the City Council speaker, does not have a campaign site, but she has reserved a domain name, according to a campaign spokesman. (And no, it’s not christinequinn.com, which is the domain of one of Ms. Quinn’s critics, or quinnforny.com, which is the site for Assemblyman Jack Quinn, a Republican from Western New York who is running for State Senate.)

John C. Liu, the city comptroller, also does not appear to have a campaign site, though one site is directed automatically to his government site.

Tom Allon, a newspaper publisher, is more up front on his Web site,tomallonformayor.com: he’s running for mayor.

And then there’s Anthony D. Weiner, the former Congressman, who was once considered the front runner. His campaign Web site is still available, but it was last updated on May 25, just a few days before news broke about an online messaging scandal that would eventually force him to resign from office.