"if windows.width less than" doesn't work

i have this code and i'm trying to make it work.

Basically, if the screen is less than 480px wide, is resizes the height of the #page div and centers it vertically. Else, if the width is wider, is just centers it vertically.

jQuery(document).ready(function(){
var wwidth = jQuery(window).width();
   if (wwidth <= 480) {
     function thirty_pc() {
     var height = jQuery(window).innerHeight();
     var thirtypc = ((95 * height) / 100) - 40;
     var topmargin = (height - thirtypc - 40) / 2;
     thirtypc = parseInt(thirtypc) + 'px';
     topmargin = parseInt(topmargin) + 'px';
     jQuery("#page").css('height',thirtypc);
     jQuery("#page").css('margin-top',topmargin);
     }

    thirty_pc();
    jQuery(window).bind('resize', thirty_pc);

   } else {
     function thirty_pc() {
     var height = jQuery(window).innerHeight();
     var pageheight = jQuery("#page").height()
     var thirtypc = (height - pageheight - 60);
     var topmargin = (thirtypc / 2);
     thirtypc = parseInt(thirtypc) + 'px';
     topmargin = parseInt(topmargin) + 'px';
     jQuery("#page").css('margin-top',topmargin);
     }

    thirty_pc();
    jQuery(window).bind('resize', thirty_pc);
}});

However, it doesn't fire when windows.width is less than 480px... cannot understand why.