As either Alexis or Aaron of reddit said "it's just a website, it's just a list of links."

In building our startup I haven't come across any monumental, super mathematically/computer science involved problems, but it's still been extremely challenging and fun. I'd say the challenge/fun comes more from trying to do all the things you listed at once, instead of any one of them singularly.

If nothing else, CSS and IE will teach you patience.