Which shouldn't work in HTML or XHTML (see below). But some browsers
may guess what you mean, some of the time.
You can in XHTML 1.0 Transitional.
You can't in XHTML 1.0 Strict or XHTML 1.1 (nor in HTML 4/4.01
Strict).
CSS is the way to go, the exact code would depend on what you content
really is but the first of the three examples given by RtS will, most
surprisingly, work in many cases.
<p style="text-align:center">
Wow. That's actually correct syntax and will centre the image. But,
and this is a question for the OP, is a single image really a
paragraph?
<p style="margin:nn%>
where nn is an appropriate number.
Only if the image itself has a % width. Because margin: 30%; with a
200px wide image will only be centred if the window is exactly 500px
wide. Also margin: 0 30%; would make more sense
align="middle" is purely for tables.
No it's not. The only elements for which align="middle" is valid are
APPLET, IFRAME, IMG, INPUT and OBJECT where it aligns the element to
the vertical middle of the line which contains it.
The align attribute of tables can take the values left, center or
right. Perhaps you're confused with the valign attribute of certain
table child elements?
Steve