Nowadays to develope a website you always need to test it on different devices like Iphones, Ipads,etc.
If you work locally with MAMP like I do, you will need to access your sites locally instead of making them live to be able to test them with your phone.
In order to do that, you can follow this great tutorial by Benjamin Rojas, that will explain very easily how to do it.
Basically , you need to install Squidman and configure it on your local server machine. Then you set up your devices to use that ip as HTML proxy and voila! You can access your local server in your local network.