FireFox和IE兼容的,己经被我搞出来了,还差Opera的:
document.getElementById("FCKeditor1___Frame").contentWindow.document.getElementsByTagName("iframe")[0].contentWindow.document.getElementsByTagName("body")[0].innerHTML
document.getElementById("FCKeditor1___Frame").contentWindow.document.getElementsByTagName("iframe")[0].contentWindow.document.getElementsByTagName("body")[0].innerHTML
IE5要用window.frames[ xx ]
或者document.all[xx]