过滤html标记 以及 返回顶部

//过滤<pre > </pre>
        str = Regex.Replace(str, @"\<(pre)[^>]*>|<\/pre>", "", RegexOptions.IgnoreCase);

//返回顶部
var BROWSER = {};
var USERAGENT = navigator.userAgent.toLowerCase();
browserVersion({ 'ie': 'msie', 'firefox': '', 'chrome': '', 'opera': '', 'safari': '', 'mozilla': '', 'webkit': '', 'maxthon': '', 'qq': 'qqbrowser' });
if (BROWSER.safari) {
    BROWSER.firefox = true;
}
BROWSER.opera = BROWSER.opera ? opera.version() : 0;
if (BROWSER.ie) {

    document.documentElement.addBehavior("#default#userdata");
}

function browserVersion(types) {
    var other = 1;
    for (i in types) {
        var v = types[i] ? types[i] : i;
        if (USERAGENT.indexOf(v) != -1) {
            var re = new RegExp(v + '(\\/|\\s)([\\d\\.]+)', 'ig');
            var matches = re.exec(USERAGENT);
            var ver = matches != null ? matches[2] : 0;
            other = ver !== 0 && v != 'mozilla' ? 0 : other;
        } else {
            var ver = 0;
        }
        eval('BROWSER.' + i + '= ver');
    }
    BROWSER.other = other;
}

//ie6下滚动问题
function ScrollTopByIE6() {
    var isie6 = window.XMLHttpRequest ? false : true;
    if (isie6)
        $('scrolltop').style.position = 'absolute';
}

window.onscroll = function() {

   //ie6下滚动问题

    ScrollTopByIE6();
    if ($('scrolltop') != null) {
        if (document.documentElement.scrollTop == 0 && document.body.scrollTop == 0)
            $('scrolltop').style.display = 'none';
        else {
            if (BROWSER.ie && BROWSER.ie < 7) {
                var viewPortHeight = parseInt(document.documentElement.clientHeight);
                var scrollHeight = parseInt(document.body.getBoundingClientRect().top);
                $('scrolltop').style.top = viewPortHeight - scrollHeight - 60 + 'px';
            }
            $('scrolltop').style.display = 'block';
        }
    }
}

function setScrollToTop(id) {
    window.scroll(0, 0);
    $(id).style.display == '' ? 'none' : '';
}
    <style>
        .scrolltop
        {
            background-image: url(images/bbsdetails/gotop.gif);
            background-repeat: no-repeat;
            background-position: 0 0;
            display: none;
            height: 58px;
            overflow: hidden;
             18px;
            line-height: 140px;
            position: fixed;
            bottom: 120px;
        }
    </style>
    <a id="scrolltop" href="javascript:;" style="left: 1200px;" class="scrolltop" onclick="setScrollToTop(this.id);">  TOP</a>