textarea元素IE6/7/8/9/10中默认有上下滚动条

IE下有上下滚动条。其它浏览器没有。先看一个示例

<!DOCTYPE HTML>
<HTML>
    <HEAD>
        <meta charset="utf-8" />
        <title>textarea</title>
    </HEAD>
    <BODY>
        <textarea></textarea>
    </BODY>
</HTML>

textarea没有任何样式，IE6/7/8/9/10下如下

圈住部分可以看到出现了上下滚动条。其它浏览器则没有。在看看overflow的值，

<!DOCTYPE HTML>
<HTML>
    <HEAD>
        <meta charset="utf-8" />
        <title>textarea</title>
    </HEAD>
 
    <BODY>
        <textarea></textarea>
        <script>
            function getStyleProperty(el, name) {
                var cssStyleDeclaration, val;
                if(window.getComputedStyle) {
                    cssStyleDeclaration = window.getComputedStyle(el, null);
                }else{
                    cssStyleDeclaration = el.currentStyle;
                }
                return cssStyleDeclaration.getPropertyValue(name);
            }
            var area = document.getElementsByTagName('textarea')[0];
            var overflowVal = getStyleProperty(area, 'overflow');
            alert(overflowVal);
        </script>
    </BODY>
</HTML>