display: none css not working on one of my pages

display: none css not working on one of my pages

I am trying to hide a loading gif for ajax. On the first two pages I have my hidden: none set in css like:

#preloader{
display:none;
}

then the div looks like:

print " <div id=\"preloader\"> <p class=\"center\"> <img src=\"ajax.gif\" alt=\"AJAX loader\" title=\"AJAX loader\" /> </p> </div>";

I am using php, that why its print and all the back slashes. But for some reason non of my divs are being hidden and I can not for the life of me figure it out. 

ANy idea what could be causing this problem?