<form action="search.php" name="sform" method="get" class="sform">
  <div class="setextout">
    <input type="text" name="setext" value="" class="setext"/>
  </div>
  <div class="sebtnout">
    <input type="button" name="Sevalue" value="谷歌" class="sbtn" onclick="onfirst(this);"/>
    <input type="button" name="Sevalue" value="百度" class="sbtn" onclick="onfirst(this);"/>
  </div>
</form>
<!--header --> 

<script>
function onfirst(obj) {
    var tex = document.sform.setext.value;
    //var decide=document.sform.Sevalue.value; //name值为Sevalue的按钮有两个，这样取值显然是错误的
    var decide = obj.value;
    alert(decide);
    var link;
    if (decide == "百度") {
        link = "http://www.baidu.com/s?wd=" + tex;
    }
    else if (decide == "谷歌") {
        link = "http://www.google.com.hk/search?q=" + tex;
    }
    window.open(link);
}

</script>