function CreateAjaxObject(){
      var http_request = false;
      if (window.XMLHttpRequest) { // Mozilla, Safari,...
         http_request = new XMLHttpRequest();
         if (http_request.overrideMimeType) {
         	// set type accordingly to anticipated content type
            //http_request.overrideMimeType('text/xml');
            http_request.overrideMimeType('text/html');
         }
      } else if (window.ActiveXObject) { // IE
         try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
         } catch (e) {
            try {
               http_request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
         }
      }
      if (!http_request) {
         alert('Cannot create XMLHTTP instance');
         return false;
      }
	return http_request;
}

function DoAjaxPost(url, parameters, callback)
{
	var http_request = CreateAjaxObject();
	http_request.onreadystatechange = function(){
		if(http_request.readyState == 4){
			if(callback != null)
				callback(http_request.status,result = http_request.responseText);
		}else{
			//alert("Ajax call failed");
		}
	};
	if( parameters != null ){
		http_request.open('POST', url, true);
		http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		http_request.setRequestHeader("Content-length", parameters.length);
	}else{
		http_request.open('GET', url, true);
	}
    http_request.setRequestHeader("Connection", "close");
    http_request.send(parameters);
}

function SafeUrlEncode(plaintext){
	var SAFECHARS = "0123456789" +					// Numeric
					"ABCDEFGHIJKLMNOPQRSTUVWXYZ" +	// Alphabetic
					"abcdefghijklmnopqrstuvwxyz" +
					"-_.!~*'()";					// RFC2396 Mark characters
	var HEX = "0123456789ABCDEF";
	var encoded = "";
	for (var i = 0; i < plaintext.length; i++ ) {
		var ch = plaintext.charAt(i);
	    if (ch == " ") {
		    encoded += "+";				// x-www-urlencoded, rather than %20
		} else if (SAFECHARS.indexOf(ch) != -1) {
		    encoded += ch;
		} else {
		    var charCode = ch.charCodeAt(0);
			if (charCode > 255) {
			    alert( "Unicode Character '" 
                        + ch 
                        + "' cannot be encoded using standard URL encoding.\n" +
				          "(URL encoding only supports 8-bit characters.)\n" +
						  "A space (+) will be substituted." );
				encoded += "+";
			} else {
				encoded += "%";
				encoded += HEX.charAt((charCode >> 4) & 0xF);
				encoded += HEX.charAt(charCode & 0xF);
			}
		}
	} // for
	return encoded;
}

function SafeUrlDecode(encoded)
{
   // Replace + with ' '
   // Replace %xx with equivalent character
   // Put [ERROR] in output if %xx is invalid.
   var HEXCHARS = "0123456789ABCDEFabcdef"; 
   var plaintext = "";
   var i = 0;
   while (i < encoded.length) {
       var ch = encoded.charAt(i);
	   if (ch == "+") {
	       plaintext += " ";
		   i++;
	   } else if (ch == "%") {
			if (i < (encoded.length-2) 
					&& HEXCHARS.indexOf(encoded.charAt(i+1)) != -1 
					&& HEXCHARS.indexOf(encoded.charAt(i+2)) != -1 ) {
				plaintext += unescape( encoded.substr(i,3) );
				i += 3;
			} else {
				alert( 'Bad escape combination near ...' + encoded.substr(i) );
				plaintext += "%[ERROR]";
				i++;
			}
		} else {
		   plaintext += ch;
		   i++;
		}
	} // while
   return plaintext;
};

function FormToParametersString(oForm)
{
	var data = "";
	for(var i=0;i<oForm.elements.length;i++)
	{
		var element = oForm.elements[i];
		var name = escape(element.name);
		if( name == null || name == "")
			continue;
		var value;
		if(element.type == "checkbox"){
			value = element.checked?"True":"False";
		}else if(element.type == "radio"){
			if(element.checked){
				value = SafeUrlEncode(element.value);
			}else{
				continue;
			}
		}else{
			value = SafeUrlEncode(element.value);
		}
		data = data + name + "=" + value;
		if(i < oForm.elements.length-1)
			data = data + "&";
	}
//	alert(data.charAt(data.length-1));
	if(data.charAt(data.length-1) == '&')
		data = data.substring(0,data.length-1);
//  alert(data);
	return data;
}

function DoAjaxFormPost(url, oForm, callback)
{
	return DoAjaxPost(url, FormToParametersString(oForm), callback);
}