TLDR; HTML3.2 was a hellscape, don't do this to yourself.

Quote Originally Posted by gaouser View Post
1. How to stretch the inserted image of an
HTML Code:
background=""
attribute, the left blue part on seemingly default style seems to be stretched down without any CSS supporting it
Impossible.

Quote Originally Posted by gaouser View Post
2. Is there a way to mark text's background? <font> tag can change the foreground color, I had the idea of a single cell table to do it but it seems to create a newline
Close, set the cellpadding attribute of the table to 0:
HTML Code:
<table bgcolor="#FFFF00" cellspacing="0" border="0">
  <tr>
    <td><font color="red">This text has a yellow</font> background</td>
  </tr>
</table>
Quote Originally Posted by gaouser View Post
3. How to replace the bullet points <ul> use with an image? seen websites do it.
Impossible using an unordered list, you could use a table though.

Quote Originally Posted by gaouser View Post
Is there a way to set Tahoma to exactly 8px? Setting using
HTML Code:
<font size="1">
makes it smaller than 8px, and size 2 makes it larger than 8px
Impossible to specify an exact pixel size, you're totally reliant on the browser/system.