element id null issue

[blindmikey]

Hello everyone, I'm a newbie to javascript, and would absolutely love if someone could help me understand why it's returning that document.getElementById("footer") is null. What I need this to do is to add the appropriate class to the element with id="footer".

This is a php document in order to render only specific javascript depending on a variable from a cookie. If you view the link to the full script below, Everything but the problem area is working.

Code:

#Check to see if cookie has been set
if(isset($_COOKIE['isExtended']))
    { 
    #If it has, set $isExtended var to Cookie var
    $isExtended = $_COOKIE['isExtended'];
    #and echo current value
    echo "isExtended = $isExtended ;";
    #and set element's rendered class
    [COLOR="Red"]if($isExtended == 0) 
        {
        echo "document.getElementById('footer').setProperty('class','min');";
        }
        else {
        echo "document.getElementById('footer').setProperty('class','max');";
        }[/COLOR]
    }
#If it hasn't, echo default value
else 
{ 
echo "isExtended = 1 ;";
} 

Here is the link I'm working on: http://blog.blindmikey.com
And here is a direct link to the full script: http://blog.blindmikey.com/wp-conten...oterToggle.php

Thank you to anyone that can explain this to me, sad to admit, I've spent hours on this.
-mikey