It's very easy to show html or xhtml (or any code) on your website. All you do is replace the triangle brackets with asci code.

• < turns to &lt;
• > turns to &gt;

Then you type your code normally and use <br /> to make spaces between the lines.

Here is a short example:
&lt;img src="blah.gif" /&gt;

If you want to make your code look different than the normal text on your page, here's a little taste of css. Add

around the code you want to display, and then add (and feel free to edit) this code to your css:

That's all there is to it!