var iframe = document.createElement("iframe");
iframe.id = "frame-" + index;
iframe.src = url;
iframe.width = "100%";
iframe.marginwidth = "0";
iframe.scrolling = "no";
iframe.frameborder="0";
使用IE中“查看选定区域源代码”发现创建的iframe代码是<IFRAME frameborder=0/>，网上搜了下资料，原来是IE不认小写，我晕死....
使用
setAttribute("frameborder", "0", 0);
//问题解决了。
var iframe = document.createElement("iframe");
iframe.id = "frame-" + index;
iframe.src = url;
iframe.width = "100%";
iframe.marginwidth = "0";
iframe.scrolling = "no";
iframe.setAttribute("frameborder", "0", 0); //最后一个0表示是否区别大小写，问题解决