Muslim's here, Halal as in حلال and Haram as in حَرَام do not limit themselves to stuff related to food. Really it's not. I am not implying that Internet can be haram or halal, but there are things besides food that are considered either halal or haram. For example, sexual intercourse without nikah is considered haram, and the opposite is considered halal.
Thanks for correcting the mistake in the parent comment. For the uninitiated: as a simplification things you can do fall into three categories: halal (you can do it and it's a good thing), makruh (http://en.wikipedia.org/wiki/Makruh, مكروه) (smt that's not a clear sin but should best be avoided), and haram (you shouldn't do it, it's sin), these all have subclasses and it's complicated, so this is a rough guide. The non-Muslim population generally encounters only the food aspect of this distinction, due to notices on restaurants and food items.
Now, many (orthodox) Muslims would consider lusting after women who are not your wife (or wives where that applies) as haram, and see the Internet as a thing that facilitates this. This is not a new thing, e.g. the Internet is heavily filtered in Saudi Arabia. You can't subscribe to, say, Playboy from that country or have it sent to you, because they check the mail items.
Now, whether all this makes sense in year 2012 is another question.
I am sorry for not providing enough details. Nikah is a kind of procedure, analogous to the christian church procedure where priest makes the marriage lawful by christian rules, but instead the priest, we have mullahs, and instead of church we have mosques( Though if I am not mistaken, my parents had their nikah at home, which is also considered ok at least in our country). I think the wikipedia page would be the most unbiased source for you to check out if you are interested:
http://en.wikipedia.org/wiki/Marriage_in_Islam
Interesting. The Jewish equivalents of kosher (proper), parve (neutral) or treif (bad) also originally only applied to food (Kashrut dietary laws), but going as far back as the 3rd century, kosher came to mean "virtuous." It is pretty easy jump once you start talking about utensils used for food being kosher or not.
Reverse Influence from Christianity perhaps? I may have lost the faith - but I've always liked the following as a religious statement: (From Matt 15 / ESV)
You are still no more intelligent than the others.17 Don't you understand? Anything that goes into your mouth goes into your stomach and then on out of your body.18 But the things that come out of the mouth come from the heart, and these are the things that make you ritually unclean.19 For from your heart come the evil ideas which lead you to kill, commit adultery, and do other immoral things; to rob, lie, and slander others.20 These are the things that make you unclean. But to eat without washing your hands as they say you should—this doesn't make you unclean.
