The certificate expired yesterday .. you need to renew it.
Also, this in menubar.php appears to be the last issue <img style="border:0;width:88px;height:31px"
src="http://jigsaw.w3.org/css-validator/images/vcss"
alt="Valid CSS!" />
change that to <img style="border:0;width:88px;height:31px"
src="https://jigsaw.w3.org/css-validator/images/vcss"
alt="Valid CSS!" />