why is my dishwasher leaking?

I have a hotpoint first edition dishwasher that has started leaking, it has been mentioned that it could be the door seal but its not leaking from the door, it appears to be underneath. I have also read that over stacking can be a reason but how can that cause a leak.Also I read that too much detergent can cause a leak but the detergents come in a tablet so I don't understand that.Even if it was too much detergent then how would that cause a leak.