It'd be better practice to use the article sectioning elements for the news and announcement "blog" posts.
Subheadings should not be one level heading lower. They aren't really a "subtopic" in the document tree. For example:
Hyde Memorial Observatory (Heading)
Your Window to the Universe (Subhead)
http://html5doctor.com/howto-subheadings/
It's better practice to mark your navigation up in an unordered list instead of loose anchor tags.
Make sure to consistently use sectioning elements throughout your site where appropriate, like the main element for example. You only have that on the index page.
It'd be better practice to use the article sectioning elements for the news and announcement "blog" posts.
Subheadings should not be one level heading lower. They aren't really a "subtopic" in the document tree. For example: Hyde Memorial Observatory (Heading) Your Window to the Universe (Subhead) http://html5doctor.com/howto-subheadings/
It's better practice to mark your navigation up in an unordered list instead of loose anchor tags.