Say if you want to visit iPhonemactic using Safari in iPhone, there is no need to enter http:// and .com at all. Just key iPhonemactic at the address bar and hit GO and you will be channel here.
Safari will assume all web addresses that you key are ending with .com so if you need to visit websites ending other than .com, the easiest way is to tab the .com button at the bottom of the keyboard. And you will be able to see other suffix like .net, .edu, .org so you don’t have to key them in manually.