Moving 'Search' to header - help with default value

[Mooligan]

As per an older thread Greg Williams posted how he moved his search into the header. I have it up in the header now, but am not entirely sure how to make the default value in the text box to be "Enter Keywords"

 

This is the code I have in includes/header.php

<input type="text" name="keywords"  size="18" maxlength="40" value="<?php echo htmlspecialchars(StripSlashes(@$HTTP_GET_VARS["keywords"]));?>"></td> 

   <td> <?php echo tep_hide_session_id() . tep_image_submit('button_quick_find.gif', BOX_HEADING_SEARCH);?> </form></td> 

 

 

If I add in a value="Enter Keywords" it works, but it clears whatever the user had in the search box after each search and enters that back in. I want it to be there initially, but want whatever the user searches for to stay in the box after he presses search..

 

Help?