元素等高

　　　　 <div style="overflow:hidden;">
            <div style="box-sizing:content-box;float:left;50%;background:red;padding-bottom:1000px;margin-bottom:-1000px;">
                <p>iweuhfwehfwefhwfe</p>
                <p>iweuhfwehfwef</p>
                <p>iweuhfwehfw</p>
            </div>
            <div style="float:left;50%;background:blue;box-sizing:content-box;padding-bottom:1000px;margin-bottom:-1000px;">
                <p>iweuhfwehfwe</p>
                <p>iweuhfwehfwe</p>
                <p>iweuhfwehfwe</p>
                <p>iweuhfwehf</p>
                <p>iweuhfweh</p>php 
            </div>
        </div>

那个子元素矮的会被padding补齐，起到了内容等高的效果。padding-bottom与margin-bottom最好保证数值相等，padding为正，margin为父