style="display:block"用了block當然會換行了,改為inline
<html>
<head>
<title>test javascript</title>
<script language="javascript">
<!--
     
    function selType(){
         var obj=document.getElementById("change");
 
         if(obj.value=="sale"){
            sel.sett1.style.display="inline";
            sel.sett2.style.display="inline";
         }else{
            sel.sett1.style.display="none";
            sel.sett2.style.display="none";
         }
    }
-->
</script>
 
</head>
<body>
<form id="sel" name="sel" action="???" method="post">
    <select name="sale" id="change" onchange="selType()">
    <option value="sale">销售</option>
    <option value="stock">库存</option>
</select>
     
    <input type="text" id="sett1" style="display:inline" name="startdate" value="<?php echo date('Ymd',strtotime('-30 day'));?>"  size ='8' />
    -<input type="text" id="sett2" style="display:inline" name="enddate" value="<?php echo date('Ymd',strtotime('-0 day')); ?>" size='8' />
</form>   
</body>
</html>
;