Help about PHP and JScript

Hi
I need a HUGE help, because I am new to PHP and do not have much experience.

I need help regarding PHP and JScript, iframe
I have a page with html and iframe
navigation links are on the side and top, and everything opens in the iframe to the right side of navigation.
example:
HTML: KOMPAS - Bike Shop
And it works almost OK
I do not know why the thumbnail viewer displays the image only within the iframe?

For sidenav I used stu nicholls dot com | menu - Tree Frog Slide

and for thumbnail viewer Dynamic Drive DHTML Scripts- Image Thumbnail Viewer

but I tried to make the entire page in PHP, and now it works almost well
but I want sidenav to works as in the example with html

I want Sub level to remain open until I click on top level
example with PHP
PHP: KOMPAS - Bike Shop

question:
How to make that sidenav works as in the example with HTML
I want to change contents only inside "Maincontent" div?

I apologize for the bad english but I'm not the worst
Chick Point
:)

If someone needs to send the original PHP code

Thank you for reading this especially if you are able to help me out on this.