Clear your browser cache with Ctrl-F5 (i.e. hold down the Control key and then press F5)
Clear your browser cookies (search the web for docs about your specific browser)
Try another browser
Check your error log (File/folder permission problems will be typically logged here)
Are your file and folder perms ok? Run sh setup.sh if you have shell access. When you update your files, via SVN or otherwise, the file permissions may no longer be OK. -> File and Folder permissions
If you changed a server setting, did you restart Apache?
Change the theme (especially if you are using custom theme)
Try to reproduce the problem on a Tiki demo site. If you can reproduce, then, please report a bug
Activate debugging/logging tools
YAML
preferences:
error_reporting_level: 2047 #Full
error_reporting_adminonly: n #Not just for admins because we could be testing as Anonymous
smarty_notice_reporting: y
log_sql: y #logging sql queries
log_mail: y #logging sent email
log_tpl: y #add comments in templates (if you click view source, you can see which tpl was used to create it
feature_debug_console: n # [http://dev.tikiwiki.org/Debugger+Console|Debugger Console]
feature_bot_bar_debug: y
feature_debug_console: y
use_minified_scripts: n # to use compressed version of scripts, when available for faster performance but not so useful for debugging.
style: thenews.css
feature_wiki_1like_redirection: n #Tiki tries to be smart but this can be annoying because it prevents error messages on typos
You should also empty all *.tpl.php files in templates_c/
Blank pages
The most common cause of a white screen (no error message, but no content displays) is insufficient PHP script execution memory. A minimum of 16MB is required. Check your phpinfo page or contact your server admin to make sure your site meets this requirement.