select的分类选择,经测试IE和FF都能很好的支持该元素

!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
html xmlns="http://www.w3.org/1999/xhtml"
head
titleruncode/title
meta http-equiv="Content-Type" content="text/html; charset=utf-8" /
meta name="Author" content="Sheneyan" /
/head
body
select
optgroup label="a"
optiona1/option
optiona2/option
optiona3/option
/optgroup
optgroup label="b"
optionb1/option
optionb2/option
optionb3/option
/optgroup
/select
/body
/html