I use Socket Connect in my Applet. When I view my web page on other PC on the Intranet, I cannot connect successfully. An error for security reason occured . I now found the only way I can find to solve this problem: download this applet class to a certain dir add this dir to CLASSPATH in environment change system time older than this class close IE and reopen to view the webpage from the server this time It connects ok! I just don't know how this happens , any other way to solve this problem?