Microformats are semantic markup formats for (X)HTML pages that help make the content accessible for search robots. Microformats allow the webmaster to indicate the meaning of specific fragments of text explicitly by supplementing existing HTML markup with special blocks of code.
For example, you can indicate that a particular line is the address of your organization:
<div class="adr"> Moscow, 16 Leo Tolstoy Street</div>
Microformats are an open standard used by various services all over the world. At present, there are microformats for several popular subject areas, particularly for publishing information on organizations, products, reviews, events and many other things.
Yandex currently supports the following microformats:
hCard — markup format for contact information (addresses, telephone numbers, etc.);
hRecipe — format for describing cooking recipes;
hReview — markup format for reviews;
You can validate the markup on your website by using the microformats validator.
The official site for microformats is http://microformats.org/wiki/.