Font size is 10px but the system claims it is 11px

#1 

<!DOCTYPE html>
<html>
	<head>
		<title>First font size change</title>
	</head>
	<body>
		<p style="font-size: 10px">Some text for you to make tiny!></p>
		<p style="font-size: 20px">Some text for you to make normal size!></p>
		<p style="font-size: 40px">Some text for you to make super big!></p>
	</body>
</html>
#2

check your browser settings (use google if you have to), your browser has a minimum font-size setting, not allowing font-size smaller then 11px

#3

Changing the browser settings to allow smaller font sizes resolved this issue.

#4