[ycmike]

Mixpanel and it's free! https://mixpanel.com/

[submarine]

I know this sounds silly, but once people are on my site, how can I modify it without disrupting the service? (it's all php/js/html)

[ycmike]

Mixpanel should handle that. I would also look into using Optimizely if you plan on testing a lot.

[submarine]

I meant, the actual code. Right now, I'm modifying the source directly because nobody is on the site. And I just refresh the page to see the changes.

I'm guessing I should put a copy of my code somewhere else , test there, and then upload the changes when I'm donE?

[ycmike]

I see now. Yeah I am not sure about that one myself.

[submarine]

Looks cool. Can't figure out how to use it though...