QUOTE(pandy @ Jul 21 2020, 06:10 AM)

Too bad we have a temporary problem with the validator on this site ATM, otherwise we could have used that and maybe found something.
Stupid me. I have the offline version.
Here, some proper validation.
CODE
Results for C:\Users\user\Desktop\TEST\DavidLeon.html
Level of HTML: HTML 4.01 Strict
Errors
1. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 12, Character 14:
there is no attribute CHARSET for this element (in this HTML version)
2. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 12, Character 21:
required attribute CONTENT not specified
3. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 29, Character 11:
there is no attribute ID for this element (in this HTML version)
4. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 29, Character 19:
element HEADER not defined in this HTML version
5. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 40, Character 11:
there is no attribute CLASS for this element (in this HTML version)
6. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 40, Character 23:
element NAV not defined in this HTML version
7. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 107, Character 67:
there is no attribute TARGET for this element (in this HTML version)
8. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 120, Character 9:
there is no attribute ID for this element (in this HTML version)
9. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 120, Character 32:
there is no attribute DATA-BACKGROUND for this element (in this HTML version)
10. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 120, Character 41:
element MAIN not defined in this HTML version
11. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 123, Character 15:
there is no attribute CLASS for this element (in this HTML version)
12. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 123, Character 67:
there is no attribute DATA-BACKGROUND for this element (in this HTML version)
13. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 123, Character 124:
there is no attribute DATA-OVERLAY for this element (in this HTML version)
14. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 123, Character 135:
element SECTION not defined in this HTML version
15. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 137, Character 20:
there is no attribute DATA-ANIMATION for this element (in this HTML version)
16. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 142, Character 7:
element CENTER not defined in this HTML version
17. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 144, Character 9:
there is no attribute ALIGN for this element (in this HTML version)
18. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 145, Character 12:
end tag for element TR which is not open; try removing the end tag or check for improper nesting of elements
19. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 145, Character 17:
end tag for element TD which is not open; try removing the end tag or check for improper nesting of elements
21. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 149, Character 5:
end tag for CENTER omitted; possible causes include a missing end tag, improper nesting of elements, or use of an element where it is not
allowed
22. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 140, Character 0:
start tag was here
23. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 159, Character 11:
there is no attribute ID for this element (in this HTML version)
24. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 159, Character 19:
element FOOTER not defined in this HTML version
25. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 168, Character 54:
required attribute TYPE not specified
26. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 169, Character 55:
required attribute TYPE not specified
Almost all of those errors are because you really write HTML5, but you use a HTML 4.01 doctype. Lots of new stuff in HTML5, that's seen as unknown elements and attributes in HTML 4.01. Alas the WDG validator doesn't do HTML 5, since HTML 5 doesn't have a DTD.
Ignoring all the HTML 5 related errors it boils down to these, the only real errors.
CODE
16. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 142, Character 7:
element CENTER not defined in this HTML version
17. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 144, Character 9:
there is no attribute ALIGN for this element (in this HTML version)
18. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 145, Character 12:
end tag for element TR which is not open; try removing the end tag or check for improper nesting of elements
19. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 145, Character 17:
end tag for element TD which is not open; try removing the end tag or check for improper nesting of elements
21. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 149, Character 5:
end tag for CENTER omitted; possible causes include a missing end tag, improper nesting of elements, or use of an element where it is not
allowed
22. C:\Users\user\Desktop\TEST\DavidLeon.html, Line 140, Character 0:
start tag was here
They are caused by this peculiar bit with wrongly nested closing table tags and and CENTER isn't closed at all (and CENTER isn't allowed, neither in HTML5 nor in 4.01 Strict).
CODE
<div data-animation="fade-in-bottom 1.2s .4s">
<center><table width="60%"><tr><td>
<h3 class="text-light">400 Bad Request</h3>
<p align="justify" class="medium serif my-2 text-light">The 400 Bad Request error indicates that the server cannot or will not process the request due to something that is perceived to be a client error such as a malformed request syntax, invalid request message framing, or deceptive request routing.</p>
</table></tr></td>
</div>
This doesn't solve your problem either, but at least it shows there's basically nothing wrong with your HTML. Apart from the above bit and that you use the wrong doctype.