message says "sorry, site is temporarily unavailable"?

I am an entry level college student who chose to re-do my bosses website for my senior class project, the site was uploaded and fully functional, then a few weeks later I tried logging onto the site and a grey sign popped up saying .. “sorry, sorry site temporarily unavailable. ” I can’t log-in to my admin either to check the problem. I don’t know what went wrong or if I am capable of fixing it, so if any one knows I could really use a step by step answer!

florentynas.net