asp.net of C cross domain and cross domain write Cookie problem

 
//www.B.com The page to be called needs to be written P3P Head, thereby lifting IE To write Cookie The stop  
context.Response.AddHeader("P3P", "CP=CAO PSA OUR"); 

//www.A.com In addition to the ajax call www.B.com When the content is cross-domain access, need to use jsonp, In order to cooperate with its work need to add the following two sentences, generate jsonp return  
context.Response.ContentType = "text/plain"; 
context.Response.Write(string.Format("{0}('OK')", context.Request["callback"])); 

 
//jsonp The call does cross-domain access  
jQuery.ajax({ 
url: url, 
type: 'GET', 
data: data, 
dataType: 'jsonp', 
success: function (data) { 
window.location.href = toURL; 
} 
});