用php逐条读取mysql中的数据报错为什么？？

<?php
    $con = mysql_connect("localhost:3306","root","123456") or die("数据库连接失败".mysql_error());
    mysql_select_db("vote",$con) or die ("数据库选择失败".mysql_error());
    mysql_query("set names utf8");
    $a = mysql_query("select news from news");
    $b = mysql_fetch_row($a);
        while($b = mysql_fetch_row($a))
        {
            echo $b["0"].'<br>';
            echo $b["1"].'<br>';
        }
?>

为什么下面会报错？？

Notice: Undefined offset: 1 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\project\brief.php on line 25

Do you think it will 

Notice: Undefined offset: 1 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\project\brief.php on line 25

Do you think it

Notice: Undefined offset: 1 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\project\brief.php on line 25

数组越界，在你的这个php的25行