A Quick Question on Internet Download

Okay, so I know how to use a computer yeah? I mean, I can use all the basic Microsoft Office programs, navigate successfully around the Internet and do all those sorts of things. However, when it comes to the fine points of Internet download I am clueless.

We get 18gs a month, and Dad just came around telling everyone in the house (especially me and my brother) that we can't do any online games or videos or almost anything Internet-related for the next week because we used up HEAPS of our download and we're almost out. My question is, what are the activities that use up the most download? I feel a tad guilty and am not sure if it's my fault...so I want to know if I've done anything excessively that has led to this.

Much love if you can answer this, and love even if you can't :)

P.S - Yeah, I know, I could probably just google this and find out the answer, but it's so much more fun using Mibba! It's my new search engine :P

xoxo DD