Call ASPX page from MS CRM 4.0 using Javascript OnSave Event

Copy and paste the following code in OnSave event of Form in MS CRM entity

var APP_URL = "http://www.yourapplicationurl.com";
GetXMLResponse(APP_URL);

function GetXMLResponse(APP_URL)
{
try
{
xmlHttp=new ActiveXObject('Msxml2.XMLHTTP');
xmlHttp.open('POST', APP_URL + '/Validations.aspx?oId=' + crmForm.ObjectId + '&oType=DOC' , false);
xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');

xmlHttp.onreadystatechange=function()
{
if (xmlHttp.readyState==4)
{
myXmlDoc = xmlHttp.responseXML;
}
}

xmlHttp.send();

}
catch(e)
{
alert('Error in load...' + e);
}
return;
}