Firefox scrollbar weird behavior

Question

I have a simple textaera with this css rules

   textarea{  
  margin:0 auto;
  border-color:#333;
  padding:15px;     
  height:100px;
  width:600px;
  overflow-y:auto;    
}

In firefox(not in chrome) when i reach the height limit and the scrollbar show up, the lateral scrollbar goes to the top, but the cursor remain at the bottom. This is very annoying problem. Any idea