When web pages are loaded, HTTP return codes are given to indicate the status of the page. A standard HTTP 200 response indicates that the page has loaded okay. HTTP 404 means the page doesn't exist. HTTP 403 means that the user does not have the authorization to access the page, and so on.
These corresponding codes come with results on the page - whether it is the actual page loading successfully or an error message ("This page cannot be displayed", "Internal Server Error", etc). Occasionally, pages will sit and attempt contacting a server, and then the page loading will stop on either a completely blank page, or not even load a blank page - the previous page will still be displayed, no matter what is done.
There are many causes for a problem such as this; this indicates that an HTTP return code is not being given in any sense - the page is not loading properly with a 200 level code, and not even 400 level error codes are being generated or received. This could indicate a problem with the end server or a networking device in between that is refusing to relay the packets in such a way that is preventing HTTP codes from being generated.
Another reason can be because the Time To Live (TTL) of the packet has expired. If a packet gets caught in a switching loop, regardless of the state of an Exinda appliance in the path of traffic, and the TTL of the packet expires, a web server is never contacted to relay the request to so the web page will just sit on the previous page like a request had never been made.
To troubleshoot these issues, the Exinda offers ping and traceroute capabilities from the management port, via the web UI or CLI. These can determine whether or not traffic can reach the requested server. These tools are offered on the Configuration > System > Tools page.