To set the font size: <FONT SIZE=N>
N is a number between 1 (smallest) to 5 (largest).
This will probably show different effects on different browsers, so you're better off using the relative size setting, <BIG>, and <SMALL>.

To set the body and text color:

To set the background to a tesselated image:

Beginning an HTML page with a line end "\n" can sometimes make a difference between that page's displaying or not.

In the HTML block, expliciting stating the file type: <HTML Content-type: text/html>
can also be the difference between that page's displaying or not in some browsers.

A subtle error in a FORM tag can cause enormous problems, as it might well not be flagged as an error, by your server or browser. For example, this error:

<FORM ENTYPE="multipart/form-data"
<INPUT TYPE="FILE" NAME="sillyFile" size="80">

Caused the file being uploaded to not upload at all. Tracing the problem took days!
By the way. Did you notice the error?

The word ENTYPE is supposed to be ENCTYPE.