var movebox; 
window.onload = function () { 
  movebox = document.getElementById("movebox"); 
  movebox.addEventListener("mousedown", function (e) { 
    if (e.button > 0) { 
      fun2(); 
      return false; 
    } 
    e.preventDefault && e.preventDefault(); //明哥：去掉图片拖动响应 狠重要 
    gen.x = e.clientX; 
    gen.y = e.clientY; 
    gen._x = movebox.offsetLeft; 
    gen._y = movebox.offsetTop; 
    gen.dx = gen.x - gen._x; 
    gen.dy = gen.y - gen._y; 
    document.addEventListener("mousemove",fun1,false); 
    document.addEventListener("mouseup", fun2, false); 
  }, false); 
}; 
var fun1 = function (e) { 
  gen.L = e.clientX - gen.dx; 
  gen.T = e.clientY - gen.dy; 
  var timefun = function () { 
    window.getSelection().removeAllRanges(); 
    if (gen.L < 100) 
      gen.L = 100; 
    else if (gen.L > 200) 
      gen.L = 200; 
    if (gen.T < 125) 
      gen.T = 125; 
    else if (gen.T > 175) 
      gen.T = 175; 
    setLT(movebox, gen.L, gen.T); 
  }; 
  setTimeout(timefun, 2); 
}; 
var fun2 = function () { 
  document.removeEventListener("mousemove", fun1, false); 
  document.removeEventListener("mouseuo", fun2, false); 
}; 
var gen = { 
  x: null, 
  y: null, 
  _x: null, 
  _y: null, 
  dx: null, 
  dy: null, 
  L: null, 
  T:null, 
}; 
var setLT = function (dom, L, T) { 
  dom.style.left = L + "px"; 
  dom.style.top = T + "px"; 
}; 

body { 
  position:absolute; 
  margin:0; 
  padding:0; 
} 
#center{ 
  position:absolute; 
  top:200px; 
  left:300px; 
  width:400px; 
  height:400px; 
  background-color:#808080; 
} 
#black{ 
  position:absolute; 
  width:400px; 
  height:400px; 
  z-index:80; 
  background-color:#000; 
  opacity:0.6; 
} 
#bigimg{ 
  z-index:50; 
  position:absolute; 
  left:100px; 
  top:125px; 
} 
#movebox{ 
  z-index:100; 
  position:absolute; 
  width:100px; 
  height:100px; 
  left:150px; 
  top:150px; 
  overflow:hidden; 
  cursor:move; 
  background-color:#ff6a00; 
} 
#moveimg{ 
  position:absolute; 
  left:-50px; 
  top:-25px; 
}