浮动框控制及切换、banner随机数js

1.浮动置控制及切换

<div class="banner1"></div>
<div class="bot_banner">
    <a href="javascript:;" class="close" title="关闭"><img src="data:images/close.gif" alt="关闭"/></a>
    <div  style="width:990px;margin:0 auto;">
        <div class="div1"><img src="data:images/bot_bannerimg.png" /></div>
        <div class="div2">
            <div class="erweima">
            <a href="#"><img src="data:images/qrcode_s131029.png" /></a>
            <div class="erweimaimg"></div>
            </div>
            <a href="#" class="iphone"></a><a href="#" class="android"></a>
        </div>
    </div>
</div>

<style type="text/css">
*{ padding:0px; margin:0px;}
*html{background-image:url(about:blank);background-attachment:fixed;}/*解决IE6下滚动抖动的问题*/
.div1{float:left;padding:11px 0 0 15px;}
.div2{float:left;padding:11px 0 0 257px;}
.div2 a.iphone,.div2 a.android{display:inline-block;background: url(images/iphoneAndimg1.png) no-repeat;width: 175px;height: 48px;margin-right: 18px;}
.div2 .iphone{background-position: 0 0 !important;}
.div2 .iphone:hover{background-position: 0 bottom !important;}
.div2 .android{background-position: right 0 !important;}
.div2 .android:hover{background-position: right bottom !important;}
/*.div2 a:hover img{filter:alpha(opacity=90);opacity:0.9;}*/
/*.bot_banner.bg{background:none;filter:alpha(opacity=100);opacity:1;}*/
.bot_banner{ background:url(images/bot_bannerbj.png) repeat-x left bottom;position:fixed;height:71px;width:100%;left:;bottom:0px;z-index:;display:none;}
.close{float:right;margin:6px;}

.bot_banner{_position:absolute;_bottom:auto;_top:expression(eval(document.documentElement.scrollTop+document.documentElement.clientHeight-this.
offsetHeight-(parseInt(this.currentStyle.marginTop,10)||0)-(parseInt(this.currentStyle.marginBottom,10)||0)));_margin-bottom:0px;}/**/

</style>

     $(".bot_banner").hide();
        var botBanner = $('.banner1').height();
        //浮动置控制及切换
        $(window).on('scroll',function(){
            var scrollT = $(this).scrollTop();
            if(scrollT >= (botBanner - 200)){
                $(".bot_banner").slideDown(800);
            }else{
                $(".bot_banner").hide();
            }
    });

1.随机效果代码部分

//banner随机数
    var imgArr=["banner1","banner2"]
    var radom=Math.floor(Math.random() * 2)
    $(".banner1").addClass(imgArr[radom])//根据生成的随机数（0－5），从imgArr数组中得到图像名称，0表示第一

<div class="banner1"></div>
.banner1{height:438px;overflow:hidden;background:url(../images/banner1.jpg) no-repeat center top;}
.banner2{height:438px; overflow:hidden;background:url(../images/banner2.jpg) center top;}

<script type="text/ecmascript">
        var imgArr = ["1.jpg", "2.jpg", "3.jpg", "4.jpg", "5.jpg"]
        var radom = Math.floor(Math.random() * 5)
        document.getElementById("img").value = imgArr[radom];//根据生成的随机数（0－5），从imgArr数组中得到图像名称，0表示第一个
</script>

<input type="text" id="img" />
<div id="box"></div>