STEP 1: Enable Associate Port in all Firewalls
In order to communicate between your computer and Ethernet Shield, either within your LAN or worldwide, you need to enable HTTP port in all firewalls. Different people use different firewalls and each firewall has its own way to enable port, so here I show the most basic firewall that comes with your Windows
Default port for HTTP is port 80. Note: If your ISP blocks port 80 for some reasons, you can use port 81 or 8080, and remember to set up that same port in WAMP as well.
To enable that associate port in Windows Firewall, left click on Start menu and select Control Panel (setfw1.jpg) that will pop up Control Panel windows. Next, under Security section, select "Allow a program through Windows Firewall" (setfw2.jpg) which will result the pop up of "Windows Firewall Settings" (setfw3.jpg). On the Exceptions tab, left click on "Add port..." which pops up windows "Add a Port" (setfw4.jpg), in which you fill in the informations as follows:
Name: HTTP
Port number: 80
Protocol: TCP
When done, click OK and close all windows
Note: If you have more than one firewall, you need to enable this associate port in all firewalls. Please, consult your firewall provider for more informations