БЫЛО:

</pre>

<form action=test.php>
Имя: <input type=text name=nick value='$nick'>
<input type=submit>
</form>
<br>

СТАЛО:

<form action=test.php?PHPSESSID=ac4f4a45bdc893434c95dcaffb1c1811>
<input type=hidden name=PHPSESSID value='ac4f4a45bdc893434c95dcaffb1c1811'>
Имя: <input type=text name=nick value='$nick'>
<input type=submit>
</form>