Headings are normally bold-faced; that has been turned off below for this demonstration of size correspondence. MSIE and Opera interpret these sizes the same, but note that Gecko browsers and Chrome interpret Heading 6 as 11 pixels instead of 10 pixels/font size 1, and Heading 3 as 19 pixels instead of 18 pixels/font size 4 (though it's difficult to tell the difference even in a direct comparison and impossible in use). It seems Gecko also limits text to no smaller than 10 pixels under Windows, but not under Mac OS X (which also seems to have sizes between pixels!?).

Both pixel and point size specifications are not resizable in some browsers (MSIE) and thus are a problem for people with vision problems who wish to resize the type. It is preferable to use resizable type as demonstrated on other pages in this set.

As far as I'm concerned, the font size +/- notation is without merit. <font size="-1"><font size="+1"> does not result in the default size 3 but in size 4 (+1). Also, sizes -3 and +5 are no smaller/larger than their predecessors. That means the whole notation is merely redundant. It was designed for use in conjunction with <basefont>, now deprecated and not even supported by Gecko—all the more reason to abandon <font> and use styles.