HTML and CSS Reference
6.6. Creating Searchable Documents
Another extensible form of an HTML link that does not use the <a> tag
is one that causes the server to search a database for a document that
contains a user-specified keyword or words. An HTML document that con-
tains such a link is known as a searchable document.
6.6.1. The <isindex> Tag (Deprecated)
Before it was deprecated in both the HTML 4 and XHTML standards, au-
thors used to use the <isindex> tag to pass keywords along with a search
engine's URL to the server. The server then matched the keywords
against a database of terms to select the next document for display.
Today's authors mostly use forms to pass information to the server and
supporting programs. See Chapter 9 for details.