On my project (jquery 1.9.1, JQM 1.3.0) I'm having the checkbox shown like this:

checked - 

unchecked - 

and the code is very basic: 

1. <label><input type='checkbox' id='chkSendByEmail' data-mini='true' checked='checked' />This member is offline, send message also by email</label>

Now, when testing on a different project, dedicated for the checkbox it looks 100% as it should. Only in my original project it looks like the above. Any idea what can cause such malformed style?

Thanks,