/**
 * @param 
 * @arrange (512.笔记) jb51.cc
 **/
<style type="text/css">
    .imgwarp {
        text-align: center;
    }
    .imgwarp img {
        margin-left: auto;
        margin-right: auto;
    }
</style>

<div class="u" id="bdiv">
    <a href="http://" id="bt">按钮</a>
    <div id="sdiv"class="imgwarp" style="display:none;">
    内容
    </div>
</div>

/**
 * @param 
 * @arrange (512.笔记) jb51.cc
 **/
<script type="text/javascript">
    var lxf = function(selector) {
        if (window == this) {
            return new lxf(selector);
        }
        var doms = document.getElementsByTagName(selector);
        var arr = [];
        for (var i = 0; i < doms.length; i++) {
            arr.push(doms.item(i));
        }
        return this.setArray(arr);
    };
    lxf.prototype.setArray = function(arr) {
        this.length = 0;
        [].push.apply(this,arr);
        return this;
    }
    lxf.fn = lxf.prototype;
    var $ = lxf;
    //each方法
    $.fn.each = function(method) {
        for (var i = 0,l = this.length; i < l; i++) {
            method.call(this[i],i);
        }
    }
    //show方法
    $.fn.show = function() {
        this.each(function(i) {
            alert(i + ":" + this.id + ":" + this.innerHTML);
            this.style.display = "block";
        });
    }
    //执行
    $('div').show();
</script>