By using the numbers 1 through to 7 you can easily adjust the size of your font like this

<FONT SIZE="1">This is size 1 font</FONT>

<FONT SIZE="2">This is size 2 font</FONT>

<FONT SIZE="3">This is size 3 font</FONT>

<FONT SIZE="4">This is size 4 font</FONT>

<FONT SIZE="5">This is size 5 font</FONT>

<FONT SIZE="6">This is size 6 font</FONT>

<FONT SIZE="7">This is size 7 font</FONT>

You can also change the font between bigger and smaller in this manner

This is regular font <BIG>and this is bigger <BIG>and this is bigger still,</BIG><SMALL> and this font is smaller<SMALL> and this is smaller still <SMALL>and this is really small!</SMALL>