Microformats are a set of common markup patterns, and the community which helps create these patterns, that are designed for representing common structures in HTML. They are often promoted as a lightweight data standard, a bottom-up approach to the Semantic Web concept. Three of the initial microformats, XFN, hCard and hCalendar were introduced 2003 and 2004. In 2005, the approach was formalised into a website with a wiki and mailing lists. Microformats attempts to operate on a pragmatic basis, solving common real-world problems, and rejects complex abstract data frameworks. It also follows other design principles including the Pareto principle, the principle of don't repeat yourself, modularity in design and the following of the standard semantic uses of (X)HTML.
Microformats have seen wide adoption in the past few years, including uses on a large number of social networking sites, and on large sites like Google Maps, Yahoo! and Kelkoo. A wide number of interesting applications have appeared which reuse microformats in different ways, from automatically transferring telephone numbers and event listings to mobile telephones and PDAs through to reusing personal information in signup forms. The microformats community is run by Tantek Çelik, who was one of the primary driving forces behind the idea. The community is quite conservative about what it allows to be a microformat, requiring that a potential microformat proposal must demonstrate clear real world publication usage, and an actual problem that can be solved in the formalization of a microformat.