function chk_bw(){
  	this.ver=navigator.appVersion
  	this.dom=document.getElementById?1:0
    this.ie8=(this.ver.indexOf("MSIE 8")>-1 && this.dom)?1:0;
    this.ie7=(this.ver.indexOf("MSIE 7")>-1 && this.dom)?1:0;
  	this.ie6=(this.ver.indexOf("MSIE 6")>-1 && this.dom)?1:0;
    this.ie5=(this.ver.indexOf("MSIE 5")>-1 && this.dom)?1:0;
    this.sa3=(this.ver.indexOf("Safari")>-1);
    this.ie4=(document.all && !this.dom)?1:0;
  	this.ns5=(this.dom && !(this.ver.indexOf("Safari")>-1) && parseInt(this.ver) >= 5)?1:0;
  	this.ns4=(document.layers && !this.dom)?1:0;
    this.bw=(this.ie8 || this.ie7 || this.ie6 || this.ie4 || this.ns4 || this.ns5 || this.sa3 );
   	return this
}