var Popup = {
  open: function(options)
  {
  	leftPos = options.width ? (screen.width / 2)-(options.width/2) : 0;
	topPos = options.height ? (screen.height / 2)-(options.height/2) : 0;
    this.options = {
      url: '#',
      width: 300,
      height: 300,
	  left: leftPos,
	  top: topPos
    }
    Object.extend(this.options, options || {});
    window.open(this.options.url, '', 'width='+this.options.width+',height='+this.options.height+',left='+this.options.left+',top='+this.options.top+',scrollbars=yes');
  }
}