Just try emptying your browser cache. The more you surf, the more content thats cached. Each time a request is made, the cache is first looked at, to see if the requested page is stored locally from a previous visit. If it is, then a cached page will be displayed, if the page is not in the cache, then it will retrieve the contents from the server.
Now, the more pages you visit after a few hours, the more content that will need to be examined.