Inny 1 Posting Whiz in Training

How To write in a persistant cookie for this?

<script language="javascript">

function showimage()
{
if (!document.images)
return
document.images.pictures.src=
document.mygallery.picture.options[document.mygallery.picture.selectedIndex].value
}
//-->
</script>
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="100%"><form name="mygallery"><p><select
name="picture" size="1" onChange="showimage()">
<option selected value="http://i93.photobucket.com/albums/l72/2Xist_2006/greenbanner.png">Green Banner</option>
<option value="http://i93.photobucket.com/albums/l72/2Xist_2006/bluebanner.png">Blue banner</option>
<option value="http://i93.photobucket.com/albums/l72/2Xist_2006/pinkbanner.png">Pink Banner</option>
</select></p>
</form>
</td>
</tr>
<tr>
<td width="100%"><p align="center"><img src="http://i93.photobucket.com/albums/l72/2Xist_2006/greenbanner.png" name="pictures"</td>
</tr>
</table>