Originally Posted by docbert

No, it's not at all true. Prices can change quickly, most commonly due to people booking the "cheap" tickets between the times you looked.

If you need to prove this to yourself, the next time it happens go into your browsers "private browsing" mode and re-check (which will not send your existing cookies) - you'll find that the prices are the same regardless of which browser you're using.

You will find countless accounts of people claiming this occurring on the internet - it's simply a matter of people seeing a price increase, and presuming it was due to previous browsing history. There's never any proof behind it.