function setCookie(name, value, expires, path, domain, secure) { 
        var curCookie = name + "=" + escape(value) + 
                ((expires) ? "; expires=" + expires.toGMTString() : "") + 
                ((path) ? "; path=" + path : "/") + 
                ((domain) ? "; domain=" + domain : "") + 
                ((secure) ? "; secure" : "") 
document.cookie=curCookie; 
        } 
function getCookie(name) { 
        var prefix = name + "=" 
        var cookieStartIndex = document.cookie.indexOf(prefix) 
        if (cookieStartIndex == -1) 
                return null 
        var cookieEndIndex = document.cookie.indexOf(";", cookieStartIndex + prefix.length) 
        if (cookieEndIndex == -1) 
                cookieEndIndex = document.cookie.length 
        return unescape(document.cookie.substring(cookieStartIndex + prefix.length, cookieEndIndex)) 
} 
var now = new Date() 
now.setTime(now.getTime() + 6*1000) 
var jb51num=10; 
var visits = getCookie("jb51") 
if (!visits) 
        visits = 1 
else 
        visits = parseInt(visits) + 1 
if (visits>parseInt(jb51num)){ 
alert('没有内容'); 
location.href=''; 
} 
setCookie("jb51", visits, now)