4.4 [CSS-Level1-2008] Section 5.2.6, font-size
The [CSS-Level1-2008] specification states:
Section 5.2.6: On a computer screen a scaling factor of 1.5 is suggested between adjacent indexes.
IE7 Mode, IE8 Mode, and IE9 Mode (All Versions)
A fixed scaling factor of 1.5 is not used. A scaling factor of 1.2 is used in accordance with the [CSS-Level2-2009] specification section 15.7.