//Devuelve la posición absoluta de un objeto en pantalla
function getObjectRectangle(obj){
        var vleft, vtop, vwidth, vheight;
        /*if(obj.getBoundingClientRect){
                var rect = obj.getBoundingClientRect();
                vleft = rect.left-2;
                vtop = rect.top-2;
                vwidth = rect.right - rect.left;
                vheight = rect.bottom - rect.top;
        }else{*/
                vheight = obj.offsetHeight;
                vwidth = obj.offsetWidth;
                vleft=obj.offsetLeft;
                vtop=obj.offsetTop;

                var parent = obj.offsetParent;

                while(parent!=null){
                        if (parent.offsetLeft)
                                vleft += parent.offsetLeft;
                        if (parent.offsetTop)
                                vtop += parent.offsetTop;
                        parent = parent.offsetParent;
                }
        /*}*/

        return {top:vtop, left:vleft, width:vwidth, height:vheight}
}

        function getWindowSize() {
          var myWidth = 0, myHeight = 0;
          if( typeof( window.innerWidth ) == 'number' ) {
            //Non-IE
            myWidth = window.innerWidth;
            myHeight = window.innerHeight;
          } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
            //IE 6+ in 'standards compliant mode'
            myWidth = document.documentElement.clientWidth;
            myHeight = document.documentElement.clientHeight;
          } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
            //IE 4 compatible
            myWidth = document.body.clientWidth;
            myHeight = document.body.clientHeight;
          }
          return {width:myWidth, height:myHeight}
        }