Not having looked closely at your site code this is off the top of my head and may not do what you want it to.
Try adding this into the Back button code:
A normal form button would look something like this:
<INPUT TYPE="button" VALUE="Back" onClick="history.go(-1)">
The -1 bit tells the button how many pages to go back to.
Instead of using a history 'back' effect this says that when the button is clicked it will load up the specified page.
you can use it in a number of ways.
Text hyperlinks would look like this:
Food for thoguht ?