css class name

CSS Syntax

Remark Do NOT start a class name with a number!
This is only supported in Internet Explorer.

...

Do NOT start an ID name with a number!
It will not work in Mozilla/Firefox.

Firefox ignoring class names starting with a number

This is not a bug, this is actually according to the w3c specs,
which states that classes and ID's are not allowed starting
with a number.

評：雖然由於寫程式的關係，我不可能會用數字開頭命名。
it's a bad smell :p

不過，我認為允許數字開頭一點錯也沒有，因為他是 "css" 啊。