body,html{margin: 0 auto;padding: 0;height:100%;}
.containt_main{min-height: 100%;_height: 100%;position: relative;}
<div class="containt_main">
<div class=‘footer‘ style=‘ position:absolute;bottom:0;‘> </div>
</div>
一定要有html的css,containt_main的min-height: 100%;,然后footer:position:absolute;bottom:0;
原文:http://www.cnblogs.com/kaixiner/p/3608179.html