网上苦找2小时，全是不能兼容FF的，看来这种东西网上是搞不到现成的了，只能自己动手丰衣足食
现在发布出来，今后网上就有现成的供人使用了。
为了省事，少量位置用了jquery 改原生JS也很方便，谁需要就请自己修改了。
欢迎各位路过高人拍板，欢迎各位留言提供改进代码。
又改进 兼容了Chrome 下面的代码已修改成最新版
上源码了
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>js获取div编辑框，textarea，input text的光标位置，兼容FF和IE</title>
<script src="jquery-1.4.4.js" type="text/javascript"></script>
<script type="text/javascript">
//去除左右所有空格
String.prototype.trim = function () {
return this.replace(/(^\s*)|(\s*$)/g, "");
}
function getPosition(element) {
var OsObject = "";
if (navigator.userAgent.indexOf("MSIE") > 0) {
OsObject = "MSIE";
}
if (navigator.userAgent.indexOf("Firefox") > 0) {
OsObject = "Firefox";
}
if (navigator.userAgent.indexOf("Safari") > 0) {
OsObject = "Safari";
}
if (navigator.userAgent.indexOf("Camino") > 0) {
OsObject = "Camino";
}
if (navigator.userAgent.indexOf("Gecko") > 0) {
OsObject = "Gecko";
}
if (navigator.userAgent.indexOf("Chrome") > 0) {
OsObject = "Chrome";
}
var result = 0;
if (!document.selection) { //非IE浏览器
var thisTagName = null;
if ($(element).attr("tagName") != "TEXTAREA" && $(element).attr("tagName") != "INPUT") {
if ($(element).attr("tagName") == "DIV" && $(element).attr("contenteditable") == "true") {
thisTagName = window.getSelection().anchorNode.parentElement.tagName;
} //出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！
else {
thisTagName == null;
}
}
else {
if ($(element).attr("tagName") == "INPUT" && $(element).attr("type") == "text") {
thisTagName = window.getSelection().anchorNode.tagName;
}
else {
console.log(window.getSelection());
thisTagName = window.getSelection().anchorNode.tagName;
}
}
console.log(thisTagName);
if (thisTagName == "TEXTAREA" || thisTagName == "INPUT" || (thisTagName=="BODY"&&OsObject == "Chrome")) {
result = element.selectionStart
} //出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！
else if (thisTagName != null) {
if (thisTagName == element.tagName) {
if (window.getSelection().anchorNode.textContent == $(element).text()) {
result = window.getSelection().anchorOffset;
}
else {
var currentIndex = window.getSelection().anchorOffset;
var txt = "";
var txtoo = window.getSelection().anchorNode.previousSibling;
while (txtoo != null) {
txt += txtoo.textContent;
txtoo = txtoo.previousSibling;
} //出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！
result = txt.trim().length + currentIndex;
}
}
else {
var currentIndex = window.getSelection().anchorOffset;
var txt = "";
var txtoo = window.getSelection().anchorNode.parentElement.previousSibling;
while (txtoo != null) {
txt += txtoo.textContent;
txtoo = txtoo.previousSibling;
}
result = txt.trim().length + currentIndex;
}
} //出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！
else {
return 0;
}
} else { //IE
var rng;
if ($(element).attr("tagName") == "TEXTAREA" || ($(element).attr("tagName") == "INPUT" && $(element).attr("type") == "text") || ($(element).attr("tagName") == "DIV" && $(element).attr("contenteditable") == "true")) {
element.focus();
rng = document.selection.createRange();
rng.moveStart('character', -element.innerText.length);
var text = rng.text;
for (var i = 0; i < element.innerText.length; i++) {
if (element.innerText.substring(0, i + 1) == text.substring(text.length - i - 1, text.length)) {
result = i + 1;
}
}
} //出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！
else {
return 0;
}
}
return result;
}
function getValue(element) {
var pos = getPosition(element);
document.getElementById("pnum").value = pos;
}
</script>
<style type="text/css">
#Div1, #Div2
{
width: 500px;
height: 100px;
border: solid 1px black;
}
</style>
</head>
<body>
<input id="pnum" type="text" value="Hello,wellcome to test! 你好,欢迎测试!" onmouseup="getValue(this)"
style="display: block" />
<textarea cols="60" rows="10" onkeyup="getValue(this)" onmouseup="getValue(this)">Hello,wellcome to test! 你好,欢迎测试! 注意源代码开闭合标记之间不能换行，否则统计错误！</textarea>
<div id="Div1" onclick="getValue(this);" onkeyup="getValue(this);" contenteditable="true">一二三<span>四五</span>六七八<span>九零</span> 注意源代码开闭合标记之间不能换行，否则统计错误！注意div编辑框源码里面是嵌套有其他标签的，可以正常返回正确位置！</div>
<br />
<div id="Div2" onclick="getValue(this);" onkeyup="getValue(this);">一二三四五六<span>七八</span></div>
</body>
</html>