What Is an ASP File? Files created with Active Server Pages have the extension .ASP. This story is an example; take a look at the address above. With ASP files, you can activate your Web site using any combination of HTML, scripting such as JavaScript or Visual Basic?

Is It Hard to Use? I don't know about you, but whenever people start talking about doing things on the server, I start to get nervous. I think a lot about threading issues, synchronization, and generally stuff without a user interface. I assume it's going to be hard to do. Well, using ASP is about as easy as anything I've come across in years.

Aw, Mom. Not Another Object Model! I really hate doing this to you, but I'm going to have to use that overused and overcomplex term "object model" again. Here's how it works. When a browser requests an ASP file from your Web server, your Web server calls Active Server Pages to read through the ASP file, executing any of the commands contained within and sending the resulting HTML page to the browser.

A common proxy application is a caching web proxy. This provides a nearby cache of web pages and files available on remote web servers, allowing local network clients to access them more quickly or reliably. When it receives a request for a web resource (specified by a URL), a caching proxy looks for the resulting URL in its local cache. If found, it returns the document immediately. Otherwise it fetches it from the remote server, returns it to the requester and saves a copy in the cache. The cache usually uses an expiry algorithm to remove documents from the cache, according to their age, size, and access history. Two simple cache algorithms are Least Recently Used (LRU) and Least Frequently Used (LFU). LRU removes the documents that have been left the longest, while LFU removes the least popular documents.

Web proxies can also filter the content of web pages served. Some censorware applications — which attempt to block offensive web content — are implemented as web proxies. Other web proxies reformat web pages for a specific purpose or audience; for example, Skweezer reformats web pages for cell phones and PDAs. Network operators can also deploy proxies to intercept computer viruses and other hostile content served from remote web pages. A special case of web proxies are "CGI proxies." These are web sites which allow a user to access a site through them. They generally use PHP or CGI to implement the proxying functionality. CGI proxies are frequently used to gain access to web sites blocked by corporate or school proxies. Since they also hide the user's own IP address from the web sites they access through the proxy, they are sometimes also used to gain a degree of anonymity, called "Proxy Avoidance."