這是sina同事xiaoniu發現的，如下
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
</head>
<body>
<div id="02E503E2A1C011CFC85B7B701A0677EC0900000000000001"></div>
<script>
var str = '02E503E2A1C011CFC85B7B701A0677EC0900000000000001';
function bySelector(id) {
return document.querySelector('#'+id);
}
function byId(id) {
return document.getElementById(id);
}
alert(bySelector(str));
alert(byId(str));
</script>
</body>
</html>
兩個函數bySelector，byId分別通過querySelector和getElementById獲取元素.
頁面上有id為“02E503E2A1C011CFC85B7B701A0677EC0900000000000001”的元素。
結果：所有支持querySelector的浏覽器中通過bySelector均獲取不到（報錯），但通過getElementById卻可以獲取。
開始懷疑是id的字符串太長的原因導致querySelector獲取不到。真正原因卻是querySelector按css規范實現，即css標識符也不能以數字開頭。
W3 寫道
In CSS, identifiers (including element names, classes, and IDs in selectors) can contain only the characters [a-zA-Z0-9] and ISO 10646 characters U+00A0 and higher, plus the hyphen (-) and the underscore (_); they cannot start with a digit, two hyphens, or a hyphen followed by a digit. Identifiers can also contain escaped characters and any ISO 10646 character as a numeric code (see next item). For instance, the identifier "B&W?" may be written as "B\&W\?" or "B\26 W\3F".