Template:-

 This template "clears" both margins; it is often used before a header to make sure that the header will be the full width of the page. For technical XHTML details see Template talk:.

Usage
To clear both margins, type on a new line. To clear the left margin only, leaving the right margin uncleared, type. You may wish to only clear the left margin if there is an infobox to the right of the article and you do not wish to leave a large gap of white space to the left. To clear the right margin only, type.