if (!window.getComputedStyle) {
  window.getComputedStyle = function(el, pseudo) {
    this.el = el;
    this.getPropertyValue = function(prop) {
      var re = /(\-([a-z]){1})/g;
      if (prop == 'float') prop = 'styleFloat';
      if (re.test(prop)) {
        prop = prop.replace(re, function () {
          return arguments[2].toUpperCase();
        });
      }
      return el.currentStyle[prop] ? el.currentStyle[prop] : null;
    }
    return this;
  }
}

function getScreenSize() {
    var xScroll, yScroll;
    if(window.innerHeight && window.scrollMaxY) {	
      xScroll = window.innerWidth + window.scrollMaxX
      yScroll = window.innerHeight + window.scrollMaxY
    }
    else
      if(document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac
        xScroll = document.body.scrollWidth
        yScroll = document.body.scrollHeight
      }
      else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari
        xScroll = document.body.offsetWidth
        yScroll = document.body.offsetHeight
      }   

    var windowWidth, windowHeight
    if(self.innerHeight) {	// all except Explorer
      if(document.documentElement.clientWidth) {
        windowWidth = document.documentElement.clientWidth
      }
      else {
        windowWidth = self.innerWidth
      }
      windowHeight = self.innerHeight
	}
    else
      if(document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
        windowWidth = document.documentElement.clientWidth
        windowHeight = document.documentElement.clientHeight
      }
      else
        if(document.body) { // other Explorers
          windowWidth = document.body.clientWidth
          windowHeight = document.body.clientHeight
        }	

      // for small pages with total height less then height of the viewport
      if(yScroll < windowHeight){
        pageHeight = windowHeight;
      }
      else { 
        pageHeight = yScroll;
      }
	
      // for small pages with total width less then width of the viewport
      if(xScroll < windowWidth){	
        pageWidth = xScroll;		
      }
      else {
        pageWidth = windowWidth;
      }
    return [pageWidth,pageHeight]
}