What is commonly saved in a web cache to improve performance?

Web caching is a technique used to store copies of frequently accessed files from the internet on a local server or client device. This storage allows for quicker access to these files in future requests, significantly improving the performance of web browsing. By saving commonly accessed files, such as images, scripts, and web pages, the cache reduces the need to retrieve this data from the original server every time it is requested.

This efficiency not only speeds up load times but also reduces bandwidth usage, making it particularly beneficial for both users and web service providers. The other options do not pertain to common data saved in a web cache. System updates, unsolicited emails, and security protocols are generally not stored in a cache for performance enhancement. Instead, they serve different purposes and are managed through other processes and storage mechanisms.