// Get referrer
RefWebsite = document.referrer;

// Split on forward slash
part = RefWebsite.split("/");

// exchange http://www.blockthiswebsite.com/ with blocked website in all LOWER CASE letters
if ((part[2] == "www.sen123.com") || (part[2] == "sen123.com")) {
   // Redirect if RefWebsite is blocked
   parent.location = "http://micrometals.com/warning_index.html";
   
}