How can I solve W3C errors?

[gemini]

Using Streamline child theme:


I did check the W3C Markup Validation Service on ip-192.com and get 2 errors.


Error Line 243, Column 6: end tag for element "div" which is not open
</div> <div id="footer-widgeted">
This Error belongs to an empty sidebar-bottom-left div, which is correct defined.


Error Line 280, Column 6: end tag for element "div" which is not open
</div>
<div id="sidebar-bottom-left">
</div>
This Error closes a widget_nav_menu.


I see unclosed </body> and </html> tags at the bottom of the page.


This problem happens at Streamline child home pages with different customizations.

Any hint how I can solve this would be very much appreciated.