做div+css页面，不推荐使用的标签代码，请尽量不要使用这些html标签：
do not use these html elements in html pages.
presentational elements should not be used.
support for some elements has been (or will be) deprecated; they should not be used.
don't use these tags
presentational
复制代码 代码如下:
b big
hr
i
small
sub
sup
tt
deprecated
basefont
center
dir
font
isindex
menu
strike
u
unsupported and damaging in practice
tfoot
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