#pRightBody {
  width:556px; /*设定宽度*/
        text-align:left; /*文字左对齐*/
        float:left; /*浮动居左*/
        /*clear:right; /*不允许左侧存在浮动*/
  background:#E9E9E9;
        overflow:hidden; /*超出宽度部分隐藏*/
}
<div id="pRightBody">
<IFRAME MARGINHEIGHT=0 MARGINWIDTH=0 FRAMEBORDER=0
   WIDTH="100%" SCROLLING="NO" id="gongneng" name="gongneng"
   onload="javascript:{dyniframesize('gongneng');}"
   SRC="gongneng.jsp?csid=5609336"></IFRAME>
</div>

<script language="Javascript">
var getFFVersion=navigator.userAgent.substring(navigator.userAgent.indexOf("Firefox")).split("/")[1];
var FFextraHeight=getFFVersion>=0.1? 16 : 0 ;
function dyniframesize(iframename)
 {
  var pTar = null;
  if (document.getElementById)
  {
    pTar = document.getElementById(iframename);
  }
  else
  {
    eval('pTar = ' + iframename + ';');
  }  
  if (pTar && !window.opera)
  {
    pTar.style.display="block";
    if (pTar.contentDocument && pTar.contentDocument.body.offsetHeight)
    {
      pTar.height = pTar.contentDocument.body.offsetHeight+FFextraHeight;
    }
    else if (pTar.Document && pTar.Document.body.scrollHeight)
    {
      pTar.height = pTar.Document.body.scrollHeight;
    }
  }
 }
 </script>