I'm getting this validation error when I try to validate my site which is using twentyeleven theme:
Bad value category tag for attribute rel on element a: The string category is not a registered keyword or absolute URL. Whitespace in path component. Use %20 in place of spaces. …apid River Columns" rel="category tag">Rapid River Columns</a> and tagged <a h…
I found the code that writes this HTML to be in the category-template.php file in wp-includes. I can't figure out how to fix it. I tried replacing the space between 'category' and 'tag' with the %20 it suggests, but that produces even more errors.
I know that the HTML5 spec is always changing, so maybe this is the problem. However, I don't want this validation error to affect SEO. Does anybody know how much it will?