One of the problems web apps have against native apps, especially on the mobile front, is the constant need to re-download each web page on request. Ultimately, this leads to slower performance. Why if web apps only download new pages if they're actually needed, not because they're simply requested.

For example: perhaps the server can store a web page version in a cookie. Every slight change to the page on the server-side changes the version number. Now instead of the browser requesting a new page each time, why not just check the version number and have the server send the page if they're different? If the page similar, the user can just use a cached page.

I'm sure browsers doesn't necessarily have to change to accommodate changes to this, correct?