This tutorial was created on iOS 5.1.
Deleting all of the cookies saved on your iPhone is as easy as a few taps of the finger. To do so, return to Safari's Settings screen by repeating Steps 1-2 of this tutorial. Next, select the Clear Cookies and Data button (as shown in the example above).
Please note that doing so will also clear your Safari cache, which is temporary storage space on your device where recently viewed Web pages are held. Cache allows Safari to quickly load a previously visited page without having to reload the entire page and its images from the Web server on subsequent visits.