How multiple request to the same web page handled by a server side script. Let's say X and Y are accessing the same mail account from different computers, deleting or composing emails in the same account. How this type of access is handled by a server side script. Is there any way to avoid this situation. Also where should I find a clear picture about this.
It depends if it should be allowed or not.
For example if X logs in using the user name and password then Y logs in with the same from a different location, X should be forced to log off when he requests the next page.