Best Way to switch the workarea of a page w/o Frames

[Guest Claib23]

I am looking for help on the best way to switch the main part of a webpage using a menu bar. I have used frames in the past. But I am new to .asp pages. Is there a better, faster, more secure way to do this? For example, my page has a header menu and left menu bar. I don't want to have to reprogram those for every page. Is there a simple way to just change the work area in the center when a user clicks on a menu choice?