The DMK party cadres on Friday celebrated their leader M. Karunanidhi's 93rd birthday here by cutting cakes and providing welfare assistance to the poor.In his birthday message to the youth, Karunanidhi urged them to halt the erosion of values of the four pillars of democracy -- legislature, judiciary, executive and the press -- and redeem their glory.He said the four pillars of democracy are facing challenges. The pillars that should shine like gold have started to rust and their values eroded due to anti-democratic forces in our social and political fabric, he said.Meanwhile, leaders of various political parties greeted Karunanidhi on the occasion.