Many companies have firewalls to prevent outsiders from accessing their internal networks. If your computer is behind such a firewall, you may not be able to use the proxy service.
Some ISP's use firewalls or caching servers to minimize the amount of data their servers have to obtain from sites on the internet, thus increasing their apparent speed. In this situation, your browser may not be able to engage the Library's proxy server.
In either case, your system administrator should be able to clarify whether a firewall is blocking your access, and to discuss options with you.
As internet security has become a major problem, many users are choosing to run personal firewalls on their own computers. Some users have implemented firewall products such as Black Ice, Zone Alarm, and Symantec without negatively effecting their use of the proxy server. However, it is possible that the presence of a personal firewall may interfere with the browser's ability to access the proxy server.
If your browser is configured correctly but fails to engage the proxy server, this may be due to the presence of a personal firewall. If you are willing to run your system without the firewall, you may be able to determine whether this is the problem by turning the firewall off.
Some users have reported that wireless routers may also interfere with the browser's ability to access the proxy server. Clearly not all wireless routers have this effect. You may be able to determine whether the wireless router is the cause by disabling the wireless, and connecting by means of a conventional wire.
The Library is unable to provide specific recommendations for configuring wireless routers or personal firewall hardware or software.