There is a function by myself to change a searching options of a web page.

function setName(name, val)

{

	var isSet = 0;

	var url=window.location.search;

	var search = "";

	if(url.length>200){

		return 0;

	}

	var url_domain = window.location.href;

	if(url_domain.indexOf("?")!=-1){

		url_domain = url_domain.substr(0, url_domain.indexOf("?"));

	}

	if(url.indexOf("?")!=-1){ 

		var str = url.substr(1);

		strs = str.split("&"); 

		var key=new Array(strs.length);

		var value=new Array(strs.length);

		for(i=0;i<strs.length;i++){ 

     			key[i]=strs[i].split("=")[0]

     			value[i]=unescape(strs[i].split("=")[1]); 



			if(key[i]==name){

				if(value[i] == val){

					return 0;

				}

				value[i] = val;

				isSet = 1;

			}



			if(search != ""){

				search += "&";

			}

			search += key[i]+"="+value[i];

		} 

	} 

	if(isSet == 0){

		if(search != ""){

			search += "&";

		}		

		search += name+"="+val;

	}

	window.location = url_domain + "?" + search;

}