This is a caching problem. Instead of being made up of static web pages that don't change very often, our pages are actually created on the fly, every time they are requested. The data they contain is constantly changing too.
It's most likely that your web browser is displaying web pages from the cache on your computer which is why you are seeing old information. Clearing the cache of your web browser and refreshing the page will solve your problem.
If your Browser is Internet Explorer, you'll find the settings for this in the “Tools” drop-down menu. In Firefox, you will find the settings for this in the “Tools” > “Clear Recent History” menu. In Chrome, you will find the settings for this in the “Tools” > “History” menu.