<select><option value="zs">中山</option><option value="gz">广州</option><option value="zh">深圳</option><option value="zh">珠海</option></select>

         <script type="text/javascript">

               //取得<select>元素节点下的子元素的个数

               //var selectElement = document.getElementsByTagName("select")[0];

               //var size = selectElement.childNodes.length;

               //alert("select下共有"+size+"个元素");

               //取得“中山”字符串

               //var selectElement = document.getElementsByTagName("select")[0];

               //var zsElement = selectElement.firstChild;

               //var zs = zsElement.innerHTML;

               //alert(zs);

               //取得"广州"字符串

               //var selectElement = document.getElementsByTagName("select")[0];

               //var zsElement = selectElement.firstChild;

               //var gzElement = zsElement.nextSibling;

               //var gz = gzElement.innerHTML;

               //alert(gz);

               //取得"珠海"字符串

               //var selectElement = document.getElementsByTagName("select")[0];

               //var zhElement = selectElement.lastChild;

               //var zh = zhElement.innerHTML;

               //alert(zh);

               //取得"深圳"字符串

               //var selectElement = document.getElementsByTagName("select")[0];

               //var zhElement = selectElement.lastChild;

               //var szElement = zhElement.previousSibling;

               //var sz = szElement.innerHTML;

               //alert(sz);

               //删除"广州"元素

               var gzElement = document.getElementsByTagName("option")[1];

               var selectElement = gzElement.parentNode;

               selectElement.removeChild(gzElement);

         </script>