<linaaaak rel="pingaaaaback" href="pingback server">

XHTML

<link rel="pingback" href="pingback server" />

If used, the link element MUST match the appropriate form exactly (including the whitespace before the slash, for instance).

Pages MUST NOT include more than one such element, and MUST NOT include such a string matching the pattern described below unless it is intended to be the link element.

The pingback server placeholder MUST be replaced by the absolute URI of the pingback XML-RPC server. This URI MUST NOT include entities other than &, <, >, and ". Other characters that would not be valid in the HTML document or that cannot be represented in the document's character encoding MUST be escaped using the %xx mechanism as described in [RFC2396].