Rating:
We were ready to deobfuscate JavaScript, but there wasn't need to do it.
We just opened the link in Firefox with Firebug enabled. In the <body> element we saw:
<div id="a" data-a="function dafug(){if (prompt("Lets eat some ...?")=="tasty brainz")alert("Flag: tasty_humans_all_day_erry_day"); };"></div>
So, we got this flag ;)
