Ok there are two reasons:
First, for the outside world to see your page, you have
to configure your router to allow outside traffic in to port 80, as well as which computer will accept connections to 80 (the ip address of your linux box)
you can't type in 188.8.131.52 as the ip of your linux box because that is the IP of literally your router for now. that is why you get a blank page.
this is the process. your internet company assigns you an IP (184.108.40.206). This allows you to get on the internet and browse and lets others find you. When you have a router set up, the router takes this number, and makes up its own internal IP #'s for your house. These numbers usually go something like 192.168.x.x. These numbers are specific to each computer in your house.
eg. 192.168.0.5 might be your linux
if you want the outside world to see your page, you have to configure your router to open port 80 and to forward those requests to your linux box (192.168.0.2) in this example.
NOW, when people type 220.127.116.11, they will be first pointed to your router, then your router will see this as a web connection on port 80 and forward it to the specified computer (the linux box at 192.168.0.5). your linux box is ready for connections to 80 and will see this connection attempt and then display your index.html file in /var/www/html.
think of your router as a gatekeeper. Example, A visitor will ring your bell at your house (the house address is (http://18.104.22.168
)and the router will answer the door. The visitor says that he wants to see Mr. Web Page. The router will determine that this is a web connection through port 80 and will direct the visitor to room 192.168.0.5. When the visitor goes to that room, he see's the web page.
The ONLY way visitor can see the web page is by first talking to the router. so you will have to do a little research on your router and figure out how to forward connection requests for port 80 to a specific IP.
Good Luck. You will have to do consult the manual that came with the router or read up on it on the routers webpage. after you configure this, your webserver will be internet viewable.