Is this for the regular navigation of your site? Or the 'preious' and 'next' characterisitic will be according to some database order? If it is for a database 'next-or-previous' entry you should use a server side code, i.e., ask on the server side forum.
Now, if this is for the regular navigation the next button will be as any link, because you determine what should be next, that's not dynamic. And for the 'previous' button or link you will need a JavaScript like this:
<input type="button" value="go back" onclick="javascript:history.go(-1);" />
http://www.scriptingok.com/forum/viewtopic.php?f=12&t=495