css 三角实现，不用图片实现

{
_margin-bottom: 0;
height: 0;
width: 0;
font-size: 0;
line-height: 0;
border-width: 7px;
border-style: solid;
border-color: transparent transparent rgb(118, 214, 28) transparent;
_filter: chroma(color=tomato);
_border-color: tomato tomato #F6F6F9 tomato;
position: relative;
display: block;
left: 20px;
z-index: 2;
}

用这个作为钩子 <em class="arrow"></em>