Assuming that you mean update rather than upgrade then that should be immediate BUT:
All internet browsers are designed to save time and bandwidth by keeping copies of recently accessed files and using those instead of going back over the web. If you need to see a recent change you need to refresh your browser. On a PC press F5. For tablets, phones and other devices check the manual.
As an addendum to refreshing the page, some browsers won't reload the new files from a simple refresh, in which case you can try manually clearing the browsers temporary internet files/browser cache, restart the browser, and then accessing the page again will load the files for that page fresh.