Information about the snopes.com rating system.

If we tracked nothing but urban legends on snopes.com, the task of assigning truth values to all the entries would be much easier. As Jan Harold Brunvand wrote in The Vanishing Hitchhiker:
[U]rban legends must be considered false, at least in the sense that the same rather bizarre events could not actually have happened in so many localities to so many aunts, cousins, neighbors, in-laws, and classmates of the hundreds and thousands of individual tellers of the tales.
However, since this site also chronicles many items that do not fit the traditional definition of "urban legend" (e.g., trivia, rumors, hoaxes, common misconceptions, odd facts), our single rating system must be able to accommodate disparate types of entries. As a result, the colored bullets we use to classify items have slightly different meanings depending upon the nature of the entries being rated. Below are expansive definitions of the colors' meanings:

TRUE: Green bullets are used for two similar but distinct types of entries: claims that are demonstrably true, and urban legends that are based on real events. For the former, "demonstrably true" means that the claim has been established by a preponderance of (reliable) evidence; for the latter, a green bullet indicates that the legend described is based on an actual occurrence. (The word "based" is key here: many legends describe events that have taken place in real life, but those events did not occur until the related legend was already in circulation.)

MIXTURE: Multi-colored bullets identify claims which are a mixture of truth and falsehood.

UNDETERMINED: Yellow bullets generally describe disputed claims — factual items which the available evidence is too contradictory or insufficient to establish as either true or false. This category also includes claims that have a kernel of truth to them but are not literally true as stated. (For example, an entry that read "Soupy Sales was fired for asking children to send him 'little green pieces of paper' on his TV show" would fit this classification because even though Soupy Sales did make such a request, he was not fired for doing so.) Some legends also fall into this classification when it cannot be determined whether the legends preceded similar real life events, or vice-versa.

FALSE: Red bullets mark claims which cannot be established as true by a preponderance of (reliable) evidence. Some urban legends are also placed into this category because they describe events too implausible to have actually occurred, or too fantastic to have escaped mention in the media of the day.

OUTDATED: Multi-colored bullets also identify claims which were once true but have since changed status (e.g., a child listing as missing has been found, a condition that was the subject of protest has been rectified).

LEGEND: Hollow yellow bullets are the ones most commonly associated with "pure" urban legends — entries that describe plausible events so general that they could have happened to someone, somewhere, at some time, and are therefore essentially unprovable. Some legends that describe events known to have occurred in real life are also put into this category if there is no evidence that the events occurred before the origination of the legends.