帮我看看下面的代码老出错

[redtank1979]

function write_line(){

txt += "<td class=aaa name=bbb id=ccc background='images/bg.gif' onclick=\"check('0','3'); parent.asa.location='/setting.htm'\"><nobr>设置</nobr></td>";
txt += "<td><img name='b_right' src='images/right.gif' border=0></td>";

return txt;
}
<SCRIPT language=JavaScript>
write_line();
</SCRIPT>

[hrblg313]

txt += "<td><img name='b_right' src='images/right.gif' border=0></td>";
其中的+=是什么意思。是不是 =+

[hrblg313]

不好意思，记错了

[penny8386]

txt没定义。
function write_line(){
var txt = "";
txt += "<td class=aaa name=bbb id=ccc background='images/bg.gif' onclick=\"check('0','3'); parent.asa.location='/setting.htm'\"><nobr>设置</nobr></td>";
........
}