After setting up your Google Authorship to your website by either linking your content to your Google Profile Page or by a verified email address, go to Webmaster Tools.
Now, enter you website or blog URL and click "Preview". You should get something like the below image wherein your Authorship to your webpage has been successfully retrieved.
But, some time it happens that you get error messages like the below on your Extracted structured data,
Error: At least one field must be set for Hcard.
Error: Missing required field "name (fn)".
Error: Missing required hCard "author".
Follow these two steps and you can get rid of the above errors within minutes.
Step 1: Go to Blog Layout -> Edit Blog Post -> Post page options -> Tick " Posted by" option along with date and time.
Step 2: Go to Edit HTML -> Search for "post-header-line-1" using CTRL+F.
Below the "post-header-line-1" paste this,
<span class='post-author vcard'>Step 3: Save Template.
<a expr:href='data:post.authorProfileUrl' rel='author' title='author profile'>