拖放div和存储位置

i'm trying to make a drag and drop script but i'm stucked. What i want to achieve is: i want to drag elements from one side and put them inside a div. When i move the element inside that div my left and top position should be calculated from the edges of the droppable div not the entire document. so i can arrange and display dragged divs at the exact position even after refresh. My question is how can i get the position of divs and make an ajax call to store them in database. Here is my code and jsfiddle:i'm trying to make a drag and drop script but i