I get values using http get method in mypage.aspx page.This page's path is under ISV/Web/mypage.aspx.How can I access and get response this asp page from onload()
Using ajax or what ?
You would want to do an AJAX request, somewhere along the lines of
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", "http://YOURSERVER/mypage.aspx", false);
xmlhttp.send();
//do something with the result
alert(xmlhttp.responseXML.text);
See the XMLHttpRequest Object for more details