Some of my pages are blank except for these characters: 
Symptoms:
- Page is *almost* blank, except for showing these characters: 
- Installing the debug logging utility reports something like this:
PHP Warning: Cannot modify header information - headers already sent by (output started at /home/your_name/public_html/includes/languages/english/header.php:1) in xxxx on line yyyy.
Cause:
When the error message says that the problem is on line 1 of the language file, those symbols are BOM characters, which means you didn't save the language file in the right format.
Solution:
Edit the file, and save it in "UTF-8 without BOM" encoding/format.