I spent the day going through every page of my main Joomla web-site, checking for W3C XHTML 1.0 and CSS 2.12 compliance, fixing each error as I found it.
With the exception of 2 pages containing Joomla ‘wrapper’ modules, which are essentially HTML iFrames, I have succeeded. However, these wrappers do contain an onLoad() event called on the iFrame object, which is not XHTML 1.0 compliant – even in transitional form. It is needed because some browsers don’t re-size iFrames automatically, when the window is re-sized.
Therefore, I shall have to live with these 2 non-standard errors in the site, until some future Joomla finds a way around the issue.
I did some other stuff, such as making the robots.txt file ACAP compliant and adding hidden hCard code to every page.
I changed the footer also to include all these decals and yet still look good.