Most of the places I’ve worked for throughout my website building career have been pretty hot on accuracy – in design and in terms of spelling. My time at the BBC especially instilled in me a religious devotion to spelling web-words correctly.
Internet shouldn’t have an uppercase ‘i’ (unless it’s at the beginning of a sentence, as it is here). Neither television, nor radio are capitalised, so why should our medium be?
Website is all one word (and for people looking for someone to do your website it’s a good rule of thumb not to go for anyone who spells it ‘web site’ or, worse, ‘web-site’. That includes most of America).
World wide web is lower case.
Most importantly email neither has a hypen, nor a capital E. Just don’t. It’s wrong and makes you look like an amateur. You wouldn’t capitalise paper or envelope, and it’s no more a foreshortening of electronic mail than radio is of radiogramme.
Useful links: www.oed.com