A better method of changing font sizes and colors is the use of Cascading Style Sheets.

How to change the font size?
This is done with the following tag:

<font size="x">text to change</font>

"x" will be replaced by a number with a + or - sign in front of it. So let's say you wanted to make the font larger. You can use the tag with a +2, like this:

<font size="+2">I'm a big sentence now!</font>


Likewise, you can make the font smaller in the same way, using the - sign:

<font size="-2">Hey, I'm Small!</font>