say you were trying to give someone the html code for a banner. You were to put this code on the interwebs so all the member of said site can spam for you. How could you write the html with out it showing the banner?
This is a completely hypothetical situation of course.

<textarea><a href="Website.Url" border="0"><img src="Image.Url" width="468" height="60" border="0"></a></textarea>
course this is alot faster to parse
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while in the php area insert something like this.
<?php
$site="http://www.yourdomain.com/";
if($user == $logged)
{
$web = "register.php?r={$user['username']}";
}
else
{
$web = "register.php";
}
print "<textarea><a href='{$site}/{$web}' border='0'><img src='Image.Url' width='468' height='60' border='0'></a></textarea>";
?>