What is document cache? How does document cache impacts the peroformance of a webpage?

Document Cache: Document cache is a location on the user’s computer where a web browser temporarily stores downloaded web pages. This is a way to speed up page downloading times and to reduce traffic on the network.

• Using the cache saves time. However, documents stored persistently will become outdated if the original documents on the web sever changes. To guard against this, web browser checks whether a document in the cache is an up-to-date copy of the original on the server. This is a user specified option, and the most popular setting for web browser today is set to check once per session whether a document on the server has changed since the user last viewed it.
• A load testing tool must emulate web browser’s document cache.