$(document).ready(function(){
	var y = getyScroll();
	$('#mainbg').css('height', y + 'px');
});

function getyScroll(fl){
  yScroll = 0;
  var deff = 0;
  var wff = 0
  var hff = 0;
  if (window.innerHeight && window.scrollMaxY || window.innerWidth && window.scrollMaxX)
  {
    yScroll = parseInt(window.innerHeight) + parseInt(window.scrollMaxY); 
    var deff = document.documentElement;
    var wff = (deff&&deff.clientWidth) || document.body.clientWidth || window.innerWidth || self.innerWidth;
    var hff = (deff&&deff.clientHeight) || document.body.clientHeight || window.innerHeight || self.innerHeight;
    //yScroll = parseInt(yScroll) - (parseInt(window.innerHeight) - parseInt(hff));
  }else if(document.body.scrollHeight > document.body.offsetHeight || document.body.scrollWidth > document.body.offsetWidth)
  {
    yScroll = document.body.scrollHeight;
  }else 
  {
    yScroll = document.body.offsetHeight;
  }
  return yScroll;
}