font-size attribute

Type:length, percentage (calculated with respect to the current height of the font), "smaller", "larger", "xx-small", "x-small", "small", "medium", "large", "x-large", "xx-large"
Used By:All block elements
See:font line-height

The font-size attribute sets the size of the font. It can be set to either an absolute value (eg "14pt" or "28mm"), a relative value (eg "1.5em or "150%"), or can use one of the named values - "medium" is 11pt", and each smaller or larger step in either direction either increases or decreases the font size by 20%.

This sets the font size to 14pt

P { font-size:14pt; }

So does this!

BODY { font-size:7pt; }
P { font-size:200%; }	/* Could also be "2em" */