You are being given the opportunity to maneuver your way into the psyches of millions of people. Spoon-feed them your ideas. Readers will be much more willing to stay and much more willing to come back for more. Reading long selections of text this way is unbearable. Have your text take up no more than half the width of your screen.
Size does count.
When you put your text into HTML format, stick to using the default font size for most of the text on the page. This way you will be ensuring that what you are designing will be properly seen by most people. Use different sizes of text to create variation on your page. But don't forget, fonts that are too small infuriate and fonts that are too big irritate. Use both sparingly.