This element informs the reader that the document is an index document. As well as reading it, the reader may use a keyword search.
The node may be queried with a keyword search by suffixing the node address with a question mark, followed by a list of keywords separated by plus signs. See the network address format .
Note that this tag is normally generated automatically by a server. If it is added by hand to an HTML document, then the client will assume that the server can handle a search on the document. Obviously the server must have this capability for it to work: simply adding <ISINDEX> in the document is not enough to make searches happen if the server does not have a search engine!