HTML: Why is the tag not recommended for semantic markup? What are other “best practices” for designing?



HTML: Why is the tag not recommended for semantic markup?
its answer is something like this but need to more clear..
Semantic markup is XHTML that has been written to define the context of the content enclosed in the markup. This means that headers would be defined by

through

elements, paragraphs with

elements, lists with

    and
      elements, and so on. Tags that only have a meaning referring to style, such as and should be avoided in favor of tags that provide a semantic meaning along with their standard styles, such as and

      and What are other “best practices” for designing semantic web sites with (X)HTML?

      3-d web