html

<div class="ad_data_source_explain"></div>

css

.ad_data_source_explain:before{
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    border-width: 0 16px 16px 0;
    border-style: solid;
    border-color: #fff #fff #1AB394 #1AB394;
    background: #1AB394;
    display: block;
    width: 0;
    -webkit-box-shadow: 0 0 0 rgba(0,0,0,0.3), -1px 1px 1px rgba(0,0,0,0.2);
    -moz-box-shadow: 0 0 0 rgba(0,0,0,0.3), -1px 1px 1px rgba(0,0,0,0.2);
    box-shadow: 0 0 0 rgba(0,0,0,0.3), -1px 1px 1px rgba(0,0,0,0.2);
}

效果：

参考：

http://www.jq22.com/yanshi2534

http://www.jq22.com/jquery-info2534