var Overlay = {

    overlay: null,
    show : function() 
    {
        this.overlay = document.createElement("div");
   	    document.body.appendChild(this.overlay);
    
        if (document.all)
        {
            with (this.overlay.style)
   	        {
                position = "absolute";
   	            left = "0px";
                top = "0px";
                width= "100%";
                height = document.documentElement.offsetHeight + "px";
                backgroundColor = "#fff";
                zIndex = "800"; 
   	        }
            window.onscroll = function() {
                Overlay.overlay.style.top = Overlay.getScrollXY()[1];
            }
            document.body.style.overflow = "hidden";

        }
        else
        {
            with (this.overlay.style)
   	        {
   	            position = "fixed";
                left = "0px";
                right = "0px";
                top = "0px";
                height = document.documentElement.clientHeight + "px";
                backgroundColor = "#fff";
                zIndex = "800"; 
   	        }
        }
        this.setOpacity(this.overlay, 7);
        window.onresize = function() 
        {
            if (document.all)
            {
                Overlay.overlay.style.height = document.documentElement.offsetHeight + "px";
            }
            else{
                Overlay.overlay.style.height = document.documentElement.clientHeight + "px";
            }
        }
 
    },
    // where value 0-10
    setOpacity: function(element, value) 
    {
	    element.style.opacity = value/10;
	    element.style.filter = 'alpha(opacity=' + value*10 + ')';
    },
    
    
    close: function()
    {
        if (this.overlay != null && this.overlay.parentNode != null) 
            document.body.removeChild(this.overlay);
        this.overlay = null;
        window.onscroll = null;
        window.onresize = null;
    },
    
    getScrollXY: function () 
    {
		var scrOfX = 0, scrOfY = 0;
		if( typeof( window.pageYOffset ) == 'number' ) 
		{
			scrOfY = window.pageYOffset;
			scrOfX = window.pageXOffset;
		} 
		else if( document.body && ( document.body.scrollLeft || document.body.scrollTop ) ) 
		{
			//DOM compliant
			scrOfY = document.body.scrollTop;
			scrOfX = document.body.scrollLeft;
		} 
		else if( document.documentElement && ( document.documentElement.scrollLeft || document.documentElement.scrollTop ) ) 
		{
			//IE6 standards compliant mode
			scrOfY = document.documentElement.scrollTop;
			scrOfX = document.documentElement.scrollLeft;
		}
		return [ scrOfX, scrOfY ];
	}

}

function center(b)
{
    b.style.left = (document.documentElement.clientWidth - b.clientWidth) /2 + "px";
    
      var h = 0;
      if( typeof( window.innerWidth ) == 'number' ) {
        h = window.innerHeight;
      } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
        h = document.documentElement.clientHeight;
      } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
        h = document.body.clientHeight;
      }
       var scrolloffset = Overlay.getScrollXY()[1];
 
        b.style.top = (scrolloffset + (h - b.clientHeight) / 2) + "px";
}