元组的元素不可以更改，但是元组可以包含可更改的元素，其值可以更改。

A First Level Header

A Second Level Header

Now is the time for all good men to come to
the aid of their country. This is just a
regular paragraph.

The quick brown fox jumped over the lazy
dog's back.

Header 3

This is a blockquote.

This is the second paragraph in the blockquote.

This is an H2 in a blockquote

Some of these words are emphasized.
Some of these words are emphasized also.
Use two asterisks for strong emphasis.
Or, if you prefer, use two underscores instead.

• Candy.
  how to insert tap
• Gum.
• Booze.

This is an example link.

If you want your page to validate under XHTML 1.0 Strict,
you've got to put paragraph tags in your blockquotes:

For example.