Well this is apparently not a glitch, as the cause of the problem is that custom themes do not implement css for who's online script. I've included the css file for who's online script in this reply, you may do one of the followings to resolve the issue.
1. Create a new folder called css in your adoptables site root directory, and upload the file online.css to this folder. Then add this line for file inclusion inside script file online.php(around line 4 or 5):
PHP Code:
include("css/online.css");
2. Copy paste the css content within the file online.php to your template's style.css sheet.
I'd strongly recommend the first approach since this is the way Mys v1.3.x is built, in which users can define additional css with ease.