2001 1 2 Jimmy Wales and Larry Sanger launch Wikipedia, a free, online encyclopedia that is written and edited by volunteers. It is based on a web app called the wiki, which allows people to add, change, or delete content in collaboration with others. Wikipedia is the sixth most-popular site on the Web. Preventing cavities gets easier with the 3M™ ESPE™ Clinpro™ Dental Sealant that bonds to the teeth. Cured by light, the resin seals teeth to prevent decay.