KinderStart.com LLC is suing Google because, it says, the Web search company gave KinderStart's site a "zero" ranking in its PageRank system and blocked the site. KinderStart's site, which provides information about parenting and related topics, including its own specialized search page, suffered a major drop in visits as a result.

California based KinderStart.com wants to pursue the case as a class action on behalf of other Web sites that have suffered because they were blocked or given low PageRank numbers by Google.

Among other things, KinderStart said Google has defamed it, kept it from expressing itself in a public forum, and violated KinderStart's contract under Google's AdSense program, in which it carries ads distributed by Google and gets a commission when users click on them. KinderStart calls itself a competitor to Google in the specific area where it offers search results. As part of the suit, it wants Google to reveal how it comes up with its rankings.

Google said its search rankings are opinions and entitled to free-speech protection. Although rankings are based partly on a mathematical algorithm, Google also studies the quality of sites and makes subjective judgments, its lawyers said.

Google's position as a collector and arbiter of all sorts of information gives it unprecedented power, KinderStart's attorney's said in the case.

The judge's next step will be to rule on what parts of KinderStart's case, if any, can go forward.