I have a policy of trying to have the pages in my Web site validated to the highest possible standards – XHTML, or at least HTML 4.01 Transitional.
(The standard tool, which I use for this purpose is the W3C Markup Validation Service at http://validator.w3.org/.)
However, my efforts are hampered by the Google AdSense markup, which I use to display Google AdSense advertisements. Their customer service was, OF COURSE, unhelpful in providing me an XHTML-compliant version of the Google AdSense markup code, although they did provide me with instructions how to make it HTML 4.01 Transitional compliant.
Today I found that also the Paypal markup code, which implements the button for donations, is far from being XHTML-compliant.
I realize that there are incompatibilities between the various HTML standards, which prevent the same version of generated markup from complying with all of them. However, it’s high time that all those services provide us with an option to choose the desired compliance level for the markup, which they generate for us to insert into our Web pages.
I totally agree – this is a pet peeve of mine too. Do you still have those instructions?