Re: Tiki site not visualizing after putting some code
I would not upgrade to Tiki 9 yet, it has not been beta released yet. There is a 8.4 release, if that is what your are referring to (you appear to be at 8.3).
You may still have some custom code in the tiki_preferences table. Check tiki_preferences for any of these values in the "name" column:
feature_custom_html_head_content
header_custom_js
header_custom_css
feature_endbody_code
If you find any, delete the whole row (you mention that have header_custom_js in tiki_preferences, delete that row).
Your pages are failing before the </head> line is inserted, so it looks like there could still be a problem with some custom code from the "Look & Feel / Customization" tab.