Since I teach accessible standards compliant web design it was embarrassing to have pointed out that my own Blog had dozens of validation errors and accessibility problems. It is difficult to generate valid HTML code using Google's Blogger, but after considerable work,I think I have managed it now. The Blog posting in question now passes W3C HTML Validation with no errors (i hope).
I changed to a new version of Blogger recently, which may have been a
mistake. I assumed by now that Google would be generating HTML code
without errors in it. But when I replaced my hacked template with one of
Google's new ones, instead of dozens of errors, I got hundreds.
After looking at some articles on the topic, the way to avoid validation
errors seems to be to avoid Google generated code. So I cut away most of
the Google template.
At the same time I thought I would try out HTML 5. This seems to reduce
the amount of custom code Blogger generates for fixing idiosyncrasies in
particular browsers and so reduces the amount of code with validation
errors in it.
does not seem to be finding as many errors as the I am not sure if less code is being generated because HTML 5 is a better standard, more standardised browsers have been created, or so few are using it the problems have not yet been found. Also the HTML5 validationXHTML one, perhaps because HTML 5 is less rigid in its syntax, because the checker is better (not finding spurious errors) or is worse (not finding real errors).
Apart from HTML validation, there are still problems with my blog for CSS validation and Mobile compatibility (the blog only scores 64% for Mobile Web compatibility). Some of these I can't fix, such as Blooger inserting a style sheet with an error in it and settings in the HTTP header. Perhaps it is time to change to a more standards compliant blog system.