<script>
        function cmainFrame(){
            var hmain = document.getElementById("content");
            var bheight = document.documentElement.clientHeight;
            bheight=bheight-40;//减去上面的top
            //hmain .style.width = '100%';
            //alert(hmain.offsetHeight+"--"+bheight);
            if(hmain.offsetHeight<bheight){
                hmain .style.height = (bheight  - 45) + 'px';
            }
        }
        cmainFrame();
        window.onresize=function(){  
            cmainFrame();
        };
</script>

原文出处：/show_1C7NgaqYSX4.html