The HTML5 microdata standard includes both HTML markup (primarily for search engines) and a set of DOM functions (primarily for browsers). There’s no harm in including microdata markup in your web pages. It’s nothing more than a few well-placed attributes, and search engines that don’t understand the microdata attributes will just ignore them. But if you need to access or manipulate microdata through the DOM, you’ll need to check whether the browser supports the microdata DOM API.
The Doctors’ advice on SEO is to follow Google’s time-honoured guidelines: write valid, cross-browser, accessible HTML, don’t misuse markup or “cloak” with CSS, make a site with a clear hierarchy and text links, and write good content:
"Semantics is one of the most distinctive features of the Web Platform versus other application platforms. Developers usually ignore or de-prioritize such feature but the mastery of it can bring many benefits to our projects."
to produce and consume information about types of content for which HTML doesn't yet include nouns. The most prominent of these are WAI-ARIA, Microformats, and Schema.org.
Web crawlers understand some of these side-contracts,
If you don't already know, the hgroup element is obsolete in HTML5.
Advice is now provided in the HTML spec on how to mark up subheadings, subtitles, alternative titles and taglines using existing and implemented HTML features.
If you have a title with subtitle(s) or tag lines (i.e., more than one consecutive <h1>–<h6>), group them in an <hgroup>.
If you have a title with subtitle(s) and other metadata associated with the section or article, place both the <hgroup> and the metadata within a single <header> element.
When grouping headings in an <hgroup> element, the outline algorithm will mask the lowest level all but the highest level heading in the group from the resulting document outline.
It can only contain a group of <h1>–<h6> element(s), and it should be used for subtitles, alternative titles, and tag lines.
use the header, footer, main and nav elements to mark up the broad structure of the page. Doing this will make your site more accessible to real people who use some assistive technologies
Previous/next buttons (or pagination)
I would say yes to this because it is important to the overall structure and hierarchy of the blog/site
Search form
For me, a definite yes, but it is not mentioned in the spec. A search form is hugely important to the navigation of a site, particularly large sites which rely almost solely on their search engine.
Breadcrumbs
Again, I would say yes to this as well. Although breadcrumbs are not always necessary and can be used when not applicable, on large sites a breadcrumb trail can be an important navigation aid.
Breadcrumbs
Again, I would say yes to this as well. Although breadcrumbs are not always necessary and can be used when not applicable, on large sites a breadcrumb trail can be an important navigation aid.