How to solve structured data errors in blogger?

Structured Data Testing Tool

 The Structured Data Testing Tool (SDTT) provides a variety of ways to develop, test, and modify your structured markup.

You can load markup into the tool either directly or by supplying a URL. The editing environment for the tool provides these utilities to simplify markup testing:

Automatic highlighting

once you load your content in the editor, you can click on a validated field on the right of the editor to see which line in your markup produced that field. This is handy for isolating syntax errors.

Search & replace keyboard shortcuts

supports plain text and JavaScript regular expressions. The search and replace status line appears at the top of the Editor Panel.

Keyword completion of schema.org and JSON-LD keywords.

Structured data errors

1. The property blogId is not recognized by Google for an object of type BlogPosting.
2. The property postId is not recognized by Google for an object of type BlogPosting.
3. The dateModified field is recommended. Please provide a value if available.
4. A value for the headline field is required.
5. A value for the image field is required.
6. The property image_url is not recognized by Google for an object of type BlogPosting.
7. The mainEntityOfPage field is recommended. Please provide a value if available.
8. A value for the publisher field is required.

Log into your Blogger Dashboard.

2. Click Theme.

3. Click  Edit HTML.

1) The property blogId is not recognized by Google for an object of type BlogPosting.

Search the word itemprop='blogId'.  And you will see the line

<meta expr:content='data:blog.blogId' itemprop='blogId'/>

Replace by the below code

<meta expr:content='data:blog.blogId'/>

2) The property postId is not recognized by Google for an object of type BlogPosting.

Search the word itemprop='postId'.  And you will see the line

<meta expr:content='data:post.id' itemprop='postId'/>

Replace by the below code

<meta expr:content='data:post.id'/>

3) The dateModified field is recommended. Please provide a value if available.

Search the word itemprop='datePublished'.  And you will see the line contains itemprop='datePublished'.

Paste the below line after the above line

<meta expr:content='data:post.lastUpdatedISO8601' itemprop='dateModified'/>

4) A value for the headline field is required.

Search the word entry-title.  And you will see the line

<h3 class='post-title entry-title' itemprop='name'>

Replace by the below code

<h3 class='post-title entry-title' itemprop='headline'>

5) A value for the image field is required.

Search the word data:post.firstImageUrl.  And you will see the line

<b:if cond='data:post.firstImageUrl'>
     <meta expr:content='data:post.firstImageUrl' itemprop='image_url'/>
</b:if>

Replace by the below code

<div itemprop='image' itemscope='itemscope' itemtype='https://schema.org/ImageObject'>
      <b:if cond='data:post.firstImageUrl'>
        <img style='display:none;' expr:src='data:post.firstImageUrl' alt='Textual description of firstImageUrl'/>
        <meta itemprop='image' expr:content='data:post.firstImageUrl'/>
      </b:if>
      <meta itemprop='width' content='800'/> <!--Images should be at least 696 pixels wide.-->
      <meta itemprop='height' content='800'/>
</div>

6) The property image_url is not recognized by Google for an object of type BlogPosting.

Search the word itemprop='image_url'.  And you will see the line

<b:if cond='data:post.thumbnailUrl'>
     <meta expr:content='data:post.thumbnailUrl' itemprop='image_url'/>
</b:if>

Replace by the below code

<b:if cond='data:post.thumbnailUrl'>
     <meta expr:content='data:post.thumbnailUrl' itemprop='url'/>
</b:if>

7) The mainEntityOfPage field is recommended. Please provide a value if available.

Find the below code

<b:includable id='post' var='post'>
<div class='post hentry uncustomized-post-template' itemprop='blogPost' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'>

Changed to

<b:includable id='post' var='post'>
    <div class='post hentry uncustomized-post-template' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'>
      <meta itemscope='itemscope' itemprop='mainEntityOfPage'  itemType='https://schema.org/WebPage' expr:itemid='data:post.link' content= 'data:post.link : data:post.url'/>

Find another one

<b:includable id='mobile-post' var='post'>
<div class='post hentry uncustomized-post-template' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'>

Changed to

<b:includable id='mobile-post' var='post'>
   <div class='post hentry uncustomized-post-template' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'>
     <meta expr:itemid='data:post.link' content= 'data:post.link : data:post.url' itemType='https://schema.org/WebPage' itemprop='mainEntityOfPage' itemscope='itemscope'/>

8) A value for the publisher field is required.

<div itemprop='publisher' itemscope='itemscope' itemtype='https://schema.org/Organization'>
      <div itemprop='logo' itemscope='itemscope' itemtype='https://schema.org/ImageObject'>
        <!-- Schema Mods: THE FOLLOWING URL WILL FAIL - CHANGE IT -->
        <meta itemprop='url' content='http://www.myOrganization.com/OrgImage.png'/>
        <meta itemprop='width' content='600'/> <!-- Logos should be no wider than 600px. -->
        <meta itemprop='height' content='60'/> <!-- and no taller than 60px.-->
      </div>
      <meta itemprop='name' expr:content='data:blog.title'/>
</div>

Insert the code within the schema.org/BlogPosting and schema.org/WebPage code blocks

After the save and upload, then test again with the Structured Data Testing Tool