HTML.

Contents

Disable quirk mode.

<!DOCTYPE HTML>

Place in HEAD tag (CHARSET is one among of defined by http://www.iana.org/assignments/character-sets):

<meta http-equiv="Content-Type" content="text/html; charset=CHARSET">

or in HTML 5:

<meta charset="utf-8">

See:

http://www.w3.org/TR/REC-html40/charset.html#h-5.2.2

To center block-level element:

<div style="margin-left: auto; margin-right: auto; position: relative; width: 700px;">
  <div>SOME</div>
</div>

To center inline element:

<p style="text-align: center;">TEXT</p>

http://htmlbook.ru/

http://www.quirksmode.org/