My client facing a problem with their application which is deployed in JBoss 4.2.3 application server and Apache as a web server. The problem is when accessing the application by their end users, they are getting the HTTP 502 & 503 errors in Internet Explorer. It is happening only for few users. When they changed the browser to firefox everything working fine. When observed the pattern, it is happening mainly when the number of requests are high. I can't see anything in the application logs.