//gefunden auf http://www.java2s.com/Code/JavaScript/Event/MouseDragandDrop.htm
//Drag and Drop script - http://www.btinternet.com/~kurt.grigg/javascript

//var zIndex

if ( document.getElementById ){

  if ( window.opera ){
    document.write( "<input type='hidden' id='StopOperaSelectingAnythingWhilstDragging' value=' '>" );
  }

  if( !zIndex ) var zIndex = 1;
  var dragStartet = false;
  var eventClientX, eventClientY;
  var dragX, dragY;
  var dragObjekt;

  function onMausDown( e ){
    //fuer ie
    if ( !e ) e = window.event;

    //ie: typeof e.target undefined
    var temp = ( typeof e.target != "undefined" ) ? e.target : e.srcElement;
    if ( temp.tagName != "HTML"|"BODY" && temp.className != "dragclass" ){
       temp = ( typeof temp.parentNode != "undefined" ) ? temp.parentNode : temp.parentElement;
    }
    if ( temp.className == "dragclass" ){
      if ( window.opera ){
        document.getElementById( "StopOperaSelectingAnythingWhilstDragging" ).focus();
      }
      dragStartet = true;
      temp.style.zIndex = zIndex++;
      dragX = parseInt( temp.style.left + 0 );
      dragY = parseInt( temp.style.top + 0 );
      eventClientX = e.clientX;
      eventClientY = e.clientY;

      dragObjekt = temp;
      dragObjekt.startX = dragX;
      dragObjekt.startY = dragY;
      dragObjekt.positionieren = positionieren; 

      document.onmousemove = onMausMove;
      return false;
    }
  }

  function onMausMove( e ){
    //fuer ie
    if ( !e ) e = window.event;

    if ( dragStartet ){
      dragObjekt.positionieren( dragX + e.clientX - eventClientX, dragY + e.clientY - eventClientY );
      return false;
    }
  }

  function onMausUp(){
    if( !dragStartet ) return;
    if( dragObjekt.zuruecksetzen ){
      dragObjekt.positionieren( dragObjekt.startX, dragObjekt.startY );
    }
    dragStartet = false;
    document.onmousemove = null;
  }
 
  function positionieren( left, top ){
    this.style.left = left + "px";
    this.style.top = top + "px";
  }


  document.onmousedown = onMausDown;
  document.onmouseup = onMausUp;
}