If you want to open another html file in an area on the same page you could use an iframe or Ajax.
If you just want the page to scroll down to text lower down the same page after clicking a link, use an anchor. http://www.wickham43.net/generaladvice.php#anchors
For navigation bars, look at Cssplay http://www.cssplay.co.uk/menus/ but they generally open a new window from a link.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.