function f_submit(){
if(document.f.username.value=="")
{
alert("Sorry, 请填写用户名")
document.f.username.focus()
return false
}
else if(document.f.sitename.value=="")
{
alert("Sorry, 请填写站点名称")
document.f.sitename.focus()
return false
}
else if(document.f.siteurl.value=="")
{
alert("Sorry, 请填写网址")
document.f.siteurl.focus()
return false
}

else if(document.f.email.value=="")
{
alert("Sorry, 请填写EMAIL")
document.f.email.focus()
return false
}
else if(document.f.oursite.value=="")
{
alert("Sorry, 请填写您为本站做的链接的页面地址")
document.f.oursite.focus()
return false
}
else if(document.f.email.value!=""){
var checkOK = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_@.";
 var checkStr = document.f.email.value;
    for (i = 0; i < checkStr.length; i++)
    {
        ch = checkStr.charAt(i);
        for (j = 0; j < checkOK.length; j++)
        if (ch == checkOK.charAt(j))
            break;
        if (j == checkOK.length)
        {
           alert("Sorry, 您的邮箱含有非法字符")
document.f.email.focus()
return false
        }
    }
	i=checkStr.indexOf("@")
if(i==-1){
alert("Sorry, 请正确填写邮箱格式")
document.f.email.focus()
return false
  }
  	i=checkStr.indexOf(".")
if(i==-1){
alert("Sorry, 请正确填写邮箱格式")
document.f.email.focus()
return false
  }
 }
return true
}