下拉列表中 ONMOUSEOVER显示注释

HTML：<select id="selects"> <option selected="selected" id="brazil" onmouseover="tooltip(this)" onmouseout="nodisplay()" onclick="nodisplay()">巴西</option> <option id="usa" onmouseover="tooltip(this)" onmouseout="nodisplay()" onclick="nodisplay()">美国</option> <option id="chn" onmouseover="tooltip(this)" onmouseout="nodisplay()" onclick="nodisplay()">中华人民共和国</option></select><div id="tooltipBlock" style="position: block; display: none;">sdffds</div>    JAVASCRIPT： var tip = document.getElementById("tooltipBlock"); var selects = document.getElementById("selects"); function tooltip(obj) { var x = selects.offsetLeft, y = obj.offsetTop, h = obj.offsetHeight, w = selects.offsetWidth; /*tip.style.width = w + "px";  （这部分是定义显示提示的块的宽度） */ tip.style.marginLeft = x + w + "px"; tip.style.marginTop = y - 30 +  "px"; tip.style.display = "block"; tip.innerHTML = "这部分为程序传递（把数据库里相关国家资料传过来）"; } function nodisplay() { tip.style.display = "none"; }