This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
The relation between users htting the site and the connection pool is something that needs to be handled by the application. By setting a value of 10, what you are doing is obtaining 10 connections to the database. How u use these connections is dependant on how you write your code. If you think in terms of client/server where each user has their dedicated connection, then if a 100 users log in, then yes you would have a problem. If you look at web applications, most of them obtain a connection only when necessary (i.e when a db transaction is abt to be made) and release it shortly thereafter. So, 100 users might still be able to get their requests properly serviced. However, if 100 concurrent db requests are made, there could be one of two things happening - a wait time before a request is processed - an error situation.