There is no central clearing house or official registration cite for these servers. A few locations on the Web specialize in indexing Web pages. The search usually includes a document's Title, Main header, first few text lines, and sometimes author or server location information. Some sites do a more thorough search than others resulting in a more useful database. Given the dynamic nature of the Web and its vast size, the frequency that the database is re-indexed is critical to how useful the site will be.
Good sites are very busy.
Since this may or may not happen subject lists provide only a tiny fraction of the possible sources related to any given topic. Nevertheless, they are excellent starting points. Some examples are Yahoo , Galaxy , the Whole Internet Catalog , and the Clearinghouse for subject-Oriented Internet Resources . Many locations specialize in posting new, interesting, and creative URLs. While these locations do not index or organize their lists, you can frequently find useful sources here.