<H7>

The H7 (Header level 7) tag is specific for Mosaic: it's not part of any HTML standard...

Actually, this is somewhat curious: while FONT has seven size levels in standard HTML, the headers have only six. Mosaic is actually more consistent here than the standards!

Since Mosaic does not support HTML 4.0, none of the HTML 4.0 attributes apply. The only possible attribute is:

ALIGN=left|center|right