prev,#next{

border-left: 5px solid transparent;
border-right: 5px solid transparent;
position: absolute;
height: 0;
width: 0;

}

/向上三角形/

prev {

border-bottom: 5px solid #9bb40e;

}

/向下三角形/

next {

border-top: 5px solid #9bb40e;

}

left,#right {

border-bottom: 5px solid transparent;
border-top: 5px solid transparent;
position: absolute;
height: 0;
width: 0;

}

/向左三角形/

left {

   border-right: 5px solid #9bb40e;

}

/向右三角形/

right {

  border-left: 5px solid #9bb40e;

}