These conditional requests are logged by the server, but if no changes have been made there may be no file transfer. In addition to caching by web browsers such as Netscape and IE, there may be caching mechanisms put in place by your ISP or corporate network. These are typically referred to as proxy servers. Proxy servers reduce network load especially where a large number of users are involved. AOL uses caching extensively to reduce network load where millions of users may be visiting the same web sites.
Many statistical programs show hits, file transfers, pageviews, unique URLs, sites and sessions.
Others show KB transferred and information such as Code 304, Code 404 or Code 200. Here are a few definitions that should shed some light on your traffic statistics. Hits Any response a server sends to any browser. Any successful response to a request for any type of file. This includes image files as well as HTML or other web documents.