OK! Let's get started! To fix internet problems, you have to understand the network in your house. A home network is something like this:
So, basically, you have a computer linked to a router, which looks something like the black box below (maybe yours have antennas), either with a wire or using wi-fi.
A router is handles all the requests from all the computers in your house and in turn, gives the information to the modem, which looks something like this:
The modem is connected to the internet through either telephone wires or television wires.
Now, if this ever happens, the first thing you do (Obviously), is get a fire extinguisher before it lights your whole house on fire! (And if you have people in your house that you don't like, you can "accidentally" blast them too! Not that I'm encouraging anything...) The second thing to do, that is, if it still works, unplug the router for 30 seconds and plug it back in! There you go! Easy fix!
The more complicated problem is when you can't access the internet at all! It can also be frustrating if you are downloading something or having a video chat or, in a more severe case, you can't get your english homework to Mr.Gould!
Usually, if you can't get onto the internet, it's because some part of your home network isn't working and the easiest fix would be to unplug the modem and the router for 30 seconds and plug them back in. If that doesn't work, then you're going to have to read on!
If the unplugging solution didn't work, then you're going to have to check if the blue cable behind your computer is and behind your router is loose.
If that didn't work, then it's probably your computer's fault. To fix that, you need to really dig into the computer (This is easier if you have Windows XP, you can do it on vista and 7 too, but it requires more work, and if you have a mac, I got nothing for I don't have one!)
For XP: Press Start--->Control panel--->Network Connections--->Right-Click Local Area Connection---> Disable---> After 5 seconds, right-click again--->Enable (or something that's close to these steps... I don't have an English XP, so that my best english guess...) The place should look something like the one highlighted:
For Vista or 7 (Windows 7 Rules, Vista stinks so bad that I want to toss it out the window... Sorry, I had to fit that in): Right-click on Computer--->Manage--->Device Manager--->Network Adapters--->Right-Click and press disable on all the ones that are there (Presuming that you have more than one, if you don't, then just disable what you have)--->After 5 Seconds, Right-click and enable them all again. It should look something like this (You might not have what's there):
Congratulations, you have just finished the basic diagnostic of internet problems! Here is your certificate!!!

If you still have internet problems, tell your parents to call the company that provides the internet and complain! If they won't do that, then just leave me a comment and I'll try to solve your problem!
Due to people complaining about the fact that you can't view this post if your internet is not working, here's a downloadable version: Click here