Ads on a page

in includes/templates/my_own_template/templates I added the file
tpl_index_categories.php

Okay, that is a correct location.

Have you tried just adding the define file (and no custom tpl_index_categories.php) yet?

if i do that the site disapears

Okay, so we know the problem is in the define. Now to isolate it.
Try removing sections of the defined text, leaving properly formatted HTML each time, and see if one of those removals eliminates the fatal error. (Don't worry about the final function right now.)

target="_blank"><b>DVD recorders</a></b>?Here is one HTML error (not related to the blank screen issue).In a link, you open a <b> tag, then close the link before the closing </b> tag. Crossing nested tags is not allowed.
Who coded the HTML for this? It is fundamentally flawed in its organization.

Found it.
so that you'll be able to choose the best one.

Escape the apostrophe with a backslash .
so that you'll be able to choose the best one.

site does not disappear now, thanks for that, but no matter how I tweak it I can seem to get the text up on the website???

the site page (category 13) in question is:
http://www.airtightsecurityplus.com/security_equipment/dvr-remote-view

I thought the random singular/plural variable naming feature had struck again... but $current_categories_id is only used instead of $current_category_id in two places (music product-related), and these are probably typos.