It's invalid CSS because it is browser specific - it works in Firefox (MOZilla Firefox, get it? MOZ ... MOZ -moz) .. but IE/Opera/etc doesn't recognise -MOZZZZZ extensions to CSS
Also - ems...
Set your base font in the body tag, such as font-size: 1.0em which is the same as font-size: 100% ... you can use font-size: 1.2em which is 120% of the base font-size, etc.
p {
font-size: 955.2em;
color: #ff0000;
}
MOZ!