大鹏天空™

<select onchange="document.location.hash=this.value">
<option value="s1">A</option>
<option value="s2">B</option>
<option value="s3">C</option>
<option value="s4">D</option>
</select>

<div style="height:22px;overflow:hidden;">
<select id="s1">
<option>A1</option>
<option>A2</option>
</select><br>
<select id="s2">
<option>B1</option>
<option>B2</option>
</select><br>
<select id="s3">
<option>C1</option>
<option>C2</option>
</select><br>
<select id="s4">
<option>D1</option>
<option>D2</option>
</select><br>
</div>