var xmlHttp

function getContent(navButton)
{ 
	xmlHttp=GetXmlHttpObject()
	
	if (xmlHttp==null)
 	{
 		alert ("Browser does not support HTTP Request")
 		return
 	};

	var url="getContent.php"
	url=url+"?contentType="+navButton
	xmlHttp.onreadystatechange=stateChanged 
	xmlHttp.open("GET",url,true)
	xmlHttp.send(null)
};

function stateChanged() 
{ 
	if(xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
 	{ 
		if(xmlHttp.responseText != "")
		{
 			document.getElementById("MainContent").innerHTML = xmlHttp.responseText;
		}
		else
		{
			document.getElementById("MainContent").innerHTML = "No content available.";
		};
 	}; 
};

function GetXmlHttpObject()
{
	var xmlHttp=null;
	
	try
 	{
 		// Firefox, Opera 8.0+, Safari
 		xmlHttp=new XMLHttpRequest();
 	}
	catch (e)
	{
 		//Internet Explorer
 		try
 		{
  			xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  		}
 		catch (e)
  		{
  			xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  		};
 	};
	
	return xmlHttp;
};