validation

Error Line 68, Column 73: Bad value button for attribute type on
element a: Subtype missing.
      <a type="button" class="navbar-toggle nav-link"
href="/about.html">
Syntax of MIME type:
A media-type as defined in RFC 2616; that is, typically, a required
type, followed by a "/" character, followed by a required subtype,
optionally followed by one or more instances of a ";" character
followed by a parameter. Examples: text/css, text/css;charset=utf-8.
Error Line 149, Column 5: End tag br.
</br>
✉
Error Line 149, Column 5: Element br not allowed as child of element ul
in this context. (Suppressing further errors from this subtree.)
</br>
Contexts in which element br may be used:
Where phrasing content is expected.
Content model for element ul:
Zero or more li and script-supporting elements.