The <isindex> tag is used to display search strings in the current document. The tag is placed inside the <head> element.
The <isindex> tag wasn’t implemented steadily across browsers in previous versions of HTML, and it has been obsolete since then. When you put the element into <head>, the browser would understand it as an action to provide a search function for a document. But today each document is searchable since browsers have a Find feature.
The <isindex> tag is empty, which means that the closing tag isn’t required. But in XHTML, the (<isindex>) tag must be closed (<isindex/>).
Example of the HTML <isindex> tag:
<html> <head> <isindex prompt="Search a text" /> </head> </html>
|prompt||hint-text||Specifies the text string that is displayed in front of the search query input field. If this attribute is not specified, the default browser will display its own text.|
|action||URL||Specifies URL programs, which perform the search.|