I wrote a good article on this. Check my profile, I'm too lazy to look for it . I'd say about 3-7 MB's would be a good target for today's modems. Just don't put any videos or high quality music and you'll be fine.
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.