Ugh it's making me mad! Facebook will not let me see my...(more)?

Ok so every time I go onto facebook (on iPod touch)it says I haves notification..so an so has tagged you in... So I click on it then it just disappears and that same notification has been there for about 2 weeks and it just does the same thing?! What am I doing wrong?? I've been working facebook perfectly fine for like 2 years now and it's never done this.