把<script></script>放到head里点击不行，是什么原因？
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>折翼天使表现特性一：去浮动</title>
<style>
input[type=button] {
height: 32px;
font-size: 100%;
}
</style>
<script>
var flbtn = document.getElementById("float"),
button = document.getElementById("button"),
image2 = document.getElementsByTagName("img")[1];
if (flbtn && button && image2) {
var value_init = button.value;
button.onclick = function() {
if (this.value == value_init) {
image2.style.position = "absolute";
this.value = "撤销";
} else {
image2.style.position = "";
this.value = value_init;
}
};
flbtn.onclick = function() {
image2.style["cssFloat" in this.style? "cssFloat": "styleFloat"] = "left";
};
}
</script>
</head>
<body>
<img src="http://img1.sycdn.imooc.com//54447b06000171a002560191.jpg">
<img src="http://img1.sycdn.imooc.com//54447f4a0001eb7d01910256.jpg">
<img src="http://img1.sycdn.imooc.com//54447f550001ccb002560191.jpg">
<p><input type="button" id="float" value="点击第2张图片应用float:left"></p>
<p><input type="button" id="button" value="点击第2张图片应用position:absolute"></p>
</body>
</html>
