where to put revise after and other usage Joomla! 1.7

Goto

/libraries/joomla/document/html/renderer/head.php

Find

$buffer .= $tab.'<meta name="description" content="'.htmlspecialchars($documentDescription).'" />'.$lnEnd;

add anything below the line with the appropriate usage, such as

$buffer .= $tab.'<meta name="Revisit-After" content="30 days" />'.$lnEnd;

Sample here

if ($documentDescription) {
    $buffer .= $tab.'<meta name="description" content="'.htmlspecialchars($documentDescription).'" />'.$lnEnd;
    $buffer .= $tab.'<meta name="Revisit-After" content="30 days" />'.$lnEnd;
}

Usage Revise-After is not using in webmaster world today. This is just an example of usage.