8. A non-transitory, computer accessible memory medium storing program instructions for modifying a search engine, wherein the program instructions are executable by one or more processors to: create a search engine for a website, wherein said creating the search engine comprises creating search information for a plurality of webpages of the website, wherein the search information specifies a first set of information for each webpage; provide a search-customization user interface for modifying a ranking function of the search engine for the website, wherein the search-customization user interface specifies one or more first ranking factors; after the user inserts one or more first custom tags into source code of at least one webpage of the website, update the search information to include information related to the one or more custom tags, wherein the one or more custom tags are dedicated for customizing the search engine of the web site; provide the search-customization user interface for modifying the ranking function of the search engine for the web site, wherein, in addition to the one or more first ranking factors, the search-customization user interface specifies one or more additional ranking factors corresponding to the one or more first custom tags, wherein each additional ranking factor is added to the search-customization user interface for a respective first custom tag inserted into the source code; receive first user input from the user, wherein the first user input specifies modifying a relative weight of a first additional ranking factor of the one or more additional ranking factors; automatically modify the ranking function of the search engine to use the relative weight of the first additional ranking factor based on the first user input; after automatically modifying the ranking function of the search engine to use the relative weight of the first additional ranking factor, receive a search query for the website; and provide a plurality of search results using the ranking function.
9. The non-transitory, computer accessible memory medium of claim 8 , wherein the search-customization user interface comprises a slider for each ranking factor, wherein the first user input comprises user input to a first slider for the first additional ranking factor.