calculo que lo que queres hacer, no es borrar todo el historial de los usuarios, sino el de tu sitio.
para esto, podes usar los meta, que van :
Código HTML:
<HTML>
<HEAD>
<TITLE>Titulo de tu pagina/sitio <TITLE>
<META ... >
</HEAD>
<BODY>
El contenido de texto de tu sitio
<BODY>
</HTML>
fuente:
http://www.dalleh.com/HTML/Meta_Tags/meta_tags.shtml
Expires :
Código HTML:
<META HTTP-EQUIV="Expires" CONTENT="Tue, 01 Jan 1980 1:00:00 GMT">
<!-- The time of the page had expired and it tells your cache to get a fresh copy , use it as is -->
Pragma :
Código HTML:
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<!-- It tells your browser not to cache your page your browser to looks for a fresh copy each visit -->
Revisit-after :
Código HTML:
<Meta Name="revisit-after" Content="1 days">
<!-- You can ask some spiders to come back at a certain interval. The major search engines show up automatically when they get around to it, but this may help other spiders along. -->