Magento2.3 error on custom Luma default.xml

Question

We have a Magento2.3 based website that uses a custom child theme of Luma. However, having an issue getting a custom CSS file to appear in the header. However, we are getting this error after adding the call to the CSS file.

    exception(s):
      Exception #0 (Magento\Framework\Config\Dom\ValidationException): Theme layout update file
 /var/www/html/romanjules/app/design/frontend/Lumachild/luma/Magento_Theme/layout/default.xml is not valid.
Opening and ending tag mismatch: referenceContainer line 6 and body
 Line: 68
Opening and ending tag mismatch: body line 3 and page
 Line: 69
Premature end of data in tag page line 2
 Line: 70

Below is the html from the page

    <!-- Header Elements -->
    <referenceContainer name="page.wrapper">


    <move element="minicart" destination="custom.header" after="-" />

    <referenceBlock name="logo">
       <arguments>
          <argument name="logo_file" xsi:type="string">images/yd_logo.png</argument>
          <argument name="logo_img_width" xsi:type="number">200</argument>
          <argument name="logo_img_height" xsi:type="number">200</argument>
       </arguments>
    </referenceBlock>



    <!-- Header Elements End -->

    <!-- Nav Elements -->
    <referenceBlock name="catalog.topnav">
        <block class="Magento\Cms\Block\Block" name="text.links" after="catalog.topnav">
            <arguments>
                <argument name="block_id" xsi:type="string">custom_menu_after</argument>
            </arguments>
        </block>
    </referenceBlock>
    <!-- Nav Elements End-->


    <!-- Footer Elements -->
    <referenceContainer name="footer">
          <block class="Magento\Framework\View\Element\Template"
            name="customfooter"
            template="Magento_Theme::html/custom/customfooter.phtml"/>
    </referenceContainer>

    <referenceContainer name="page.wrapper">
        <container
          name="custom.footer"
          htmlTag="section"
          htmlId="custom_footer"
          after="-"
        >
             <block
              class="Magento\Framework\View\Element\Template"
              name="footer_bar"
              template="Magento_Theme::html/custom/footer-links.phtml"
            >
            </block>
        </container>
    </referenceContainer>
    <!-- Footer Elements -->
    <referenceContainer name="footer">
          <block class="Magento\Framework\View\Element\Template"
            name="customfooter"
            template="Magento_Theme::html/custom/customfooter.phtml"/>
    </referenceContainer>

    <referenceContainer name="page.wrapper">
        <container
          name="custom.footer"
          htmlTag="section"
          htmlId="custom_footer"
          after="-"
        >
             <block
              class="Magento\Framework\View\Element\Template"
              name="footer_bar"
              template="Magento_Theme::html/custom/footer-links.phtml"
            >
            </block>
        </container>
    </referenceContainer>

    <!--this is use for remove default elements -->
    <referenceBlock name="copyright" remove="true"/>
    <referenceBlock name="report.bugs" remove="true"/>
    <referenceBlock name="footer_links" remove="true"/>
    <referenceBlock name="switcher-store" remove="true"/>
    <referenceBlock name="catalog.compare.sidebar" remove="true"/>
    <referenceBlock name="form.subscribe" remove="true"/>
    <!-- Footer Elements Ends -->



</body>

Answer 1

The error shows because of You have defined the

<referenceContainer name="page.wrapper">

at the start of the file and not added the end tag of this node like

</referenceContainer>

So add the end tag or remove this tag if this not needed.