How secure is my P.C? - Knowledgeable answers only plz...?

Hi, i currently purchased and set up a Netgear RP61v4 Wired Router. - Very good quality - its working fine. I have enough technical knowledge to have been able to set it up securely and i'm sure that it IS providing a good level of protection, but...

There is this site recommended by netgear which tests your P.C in various ways such as pinging your I.P, trying to access ports etc... this is it (its safe by the way):

https://www.grc.com/x/ne.dll?bh0bkyd2

First you click on the Proceed button and it checks your I.P and tests your security (its very useful BTW).

Anyway, my system is as secure as it can be (pretty much). It gets the Super-stealthy award and says that my computer is basiccaly non-existent on the internet and it can't be attacked but...

What i want to know is, how is it that when i visit certain sites that i have never visted before - they display adverts for my local area? - Is this because they have used code to look at my ISP's IP or something?

10 Points waiting...

How secure is my P.C? - Knowledgeable answers only plz...?adware remover

When using a router such as yours, your computer basically "hides" behind it. If set up to use DHCP, your router will assign your computer (and the others in your home/office network) a local ip address such as 192.168.1.100. Your router will also be assigned a ip address by your ISP which is what other computers use to communicate with your home/office network over the internet.