One minor annoyance in iPhone's Safari is that the URL bar scrolls off the top of the screen along with the rest of the page when you scroll down a web page. As a result, in order to enter a new url, you are required to scroll all the way back up before being able to enter a new address.
Forum member dharrison9 described a very useful tip to address this issue.
1. You're at the bottom (or anywhere) of a webpage on your iPhone and want to go to the URL field.
2. Tap the top bar with the time and battery life indicator.
3. Boom! You're at the URL entry field!