ผมใช้ JavaScript:doCallAjax เรียกมาโชว์ใหน้าเว็บแล้วไม่โชว์ภาพครับ

<script language="JavaScript">
	   var HttPRequest = false;

	   function doCallAjax(url) {
		  HttPRequest = false;
		  if (window.XMLHttpRequest) { // Mozilla, Safari,...
			 HttPRequest = new XMLHttpRequest();
			 if (HttPRequest.overrideMimeType) {
				HttPRequest.overrideMimeType('text/html');
			 }
		  } else if (window.ActiveXObject) { // IE
			 try {
				HttPRequest = new ActiveXObject("Msxml2.XMLHTTP");
			 } catch (e) {
				try {
				   HttPRequest = new ActiveXObject("Microsoft.XMLHTTP");
				} catch (e) {}
			 }
		  } 
		  
		  if (!HttPRequest) {
			 alert('Cannot create XMLHTTP instance');
			 return false;
		  }
	
		    var pmeters = "ddd";

			HttPRequest.open('POST',url,true);

			HttPRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
			HttPRequest.setRequestHeader("Content-length", pmeters.length);
			HttPRequest.setRequestHeader("Connection", "close");
			HttPRequest.send(pmeters);
			
			
			HttPRequest.onreadystatechange = function()
			{

				 if(HttPRequest.readyState == 3)  // Loading Request
				  {
				   document.getElementById("mySpan").innerHTML = "Now is Loading...";
				  }

				 if(HttPRequest.readyState == 4) // Return Request
				  {			  
					  document.getElementById('mySpan').innerHTML = HttPRequest.responseText;
				  }		
				   if(HttPRequest.readyState == 5)  // Loading Request
				  {
				   document.getElementById("mySpan").innerHTML = "Now is Loading...";
				  }		
			}

	   }
	</script>

<a href="JavaScript:doCallAjax('webpage/aboutschool/symbol.php');">