If the POSITION is repeated three times (in its entirety -- no changes in capability such 'en passant' or castling possibility), then if either player claims a DRAW, then the site will grant a draw (and this is the standard rule in Chess).
You do have to claim the draw, the site will not do this automatically. Probably because the act of claiming a draw is classed as a type of 'move', and the site will not make your moves for you. 
sftac
My friend and i was playing with real 3d chess a while ago.We kept looping same moves,no one wanted to make diffrent one.So i said,if it goes like this 3 times,it's a draw.And he wasn't good with it.
When we were playing online chess today,When i was thinking my next move,i looped same move 3 times.Even machine didn't said anything,He said : It's a draw.
Anyone aware of this rules,an explanition who's wrong would be really appricated.Thank you from now..