function checkBrowser(){ 
this.ver=navigator.appVersion 
this.dom=document.getElementById?1:0 
this.ie5=(this.ver.indexOf("MSIE 5")>-1 && this.dom)?1:0; 
this.ie4=(document.all && !this.dom)?1:0; 
this.ns5=(this.dom && parseInt(this.ver) >= 5) ?1:0; 
this.ns4=(document.layers && !this.dom)?1:0; 
this.bw=(this.ie5 || this.ie4 || this.ns4 || this.ns5) 
return this 
} 
bw=new checkBrowser() 
if (this.bw != this.ie4) { 
history.forward(); 
}