Heading Tags
Remember when I said worrying about presentation was a big (
BIG) mistake when working with html?  HTML isn't about presentation.  It's about structure.
<h1></h1> main heading, only one per document in theory
<h2></h2> sub-points
<h3></h3> further stratifications
The h system goes down to h6 or so, I hardly ever use anything past h3 and prefer using bold instead.
Theoretically, search engines pay attention to what's inside the 
<h1></h1> tag (less so to what's in the 
<h2></h2> and 
<h3></h3> tags).
a href
To link to another page (my homepage, for instance):
<a href="http://paufler.net">www.paufler.net</a>
www.paufler.net
For email, it's:
<a href="mailto:paufler.net@gmail.com">paufler.net@gmail.com</a>
paufler.net@gmail.com
Whatever is between the end brackets is displayed.  It doesn't have to relate to the rest:
<a href="http://paufler.net">Best Site on the Web</a>
Best Site on the Web
Most resources use the same (roughly) 
a tag format.
An image tag is slightly different.  Note the lack of a matching closing tag.