Customizing Blogger: Placing Ads In Your Template

I've been struggling lately to place ads in my blogger template. The only thing that's really worked well is using the AdSense widget. But I've been wanting to place a banner ad in my template and blogger doesn't have a widget for that. When I have tried in the past, the size of my header has increased, but the ad won't display.

Well, I tried again today and finally got a helpful error message from blogger:

Your template could not be parsed as it is not well-formed. Please make sure all XML elements are closed properly.
XML error message: The reference to entity "o" must end with the ';' delimiter.

Once I read this I realized the templates are having an issue with the ampersand (&) in the src attribute of my iframe element. If my ad code looks like this:

<iframe src="http://rcm.amazon.com/e/cm?t=development05-20&o=1&p=48&l=ur1&category=kindle&banner=0Y98S4SYN0MXZ8260582&f=ifr" width="728" height="90" scrolling="no" border="0" marginwidth="0" style="border:none;" frameborder="0"></iframe>

Then I need to modify it like this:

<iframe src="http://rcm.amazon.com/e/cm?t=development05-20&amp;o=1&p=48&amp;l=ur1&amp;category=kindle&amp;banner=0Y98S4SYN0MXZ8260582&amp;f=ifr" width="728" height="90" scrolling="no" border="0" marginwidth="0" style="border:none;" frameborder="0"></iframe>

Notice I changed all the ampersands (&) to the entity reference for ampersand (&amp;). Once I did that everything worked. It would be nice if blogger would update their documentation.