Firstly, I find the amount of totally unnecessary jargon based options and technical hieroglyphics bewildering for such a prominent website.
It was enough that I exhausted my patience following the instructions in what proved a pointless search to find if the question had been previously asked ... and now this page.
Why must I need to know that the Validator comprises of so many weirdly named components in order to report a problem using it?
But by far the most frustratingly ridiculous feature is being repeatedly told that in order to pass validation I need to change the value of x to the suggested identical value x.
The detected DOCTYPE Declaration "<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Strict" "http://www.w3.org/TR/html4/strict.dtd">" has been suppressed and the DOCTYPE for "HTML 4.01 Strict" inserted instead, but even if no errors are shown below the document will not be Valid until you update it to reflect this new DOCTYPE.
If using a doctype override and overriding the original to the same that the doc already has, validator could indeed be a bit smarter about what it does/says about it. But then again, I don't see valid use cases for overriding the doctype declaration to the one it already is.
Note however that the error message you posted indicates that you have used an incorrect public identifier for an HTML 4.01 strict document; it should be
"-//W3C//DTD HTML 4.01//EN"
"-//W3C//DTD HTML 4.01 Strict"
FYI: If an incorrect public identifier was used then it suggests a further glitch as it came from using the Clean up Markup with HTML-Tidy option.
(In reply to comment #2)
> FYI: If an incorrect public identifier was used then it suggests a further
> glitch as it came from using the Clean up Markup with HTML-Tidy option.
I tried to reproduce this, but failed. Can you post a URL to a document with which the tidy option inserts an invalid public identifier?