I'm very sorry to tell you, but the answer is: do a modern HTML tutorial!
You should try Code Academy they have interactive course for beginners and intermediates with direct feedback. It seems you got stuck with an old HTML 3/4 book which won't do you any good.
But I also got an direkt answer for your link problem: this fiddle where you include the images as background-images and by using your classes and selectors efficiently you have to write(mostly copy+paste) very few lines if you want to add something.
You do the most with this CSS part:
.socialmedia a {
display: block; /* Because the image is probably higher than the text */
height: 50px; /* you have to set it to block and height 50px to show the image */
padding-left: 55px; /* make room for the background image(50px) and extra margin(+5px) */
padding-top: 12px; /* center in the middle of the image */
padding-bottom: 12px;
text-decoration: none;
}
Example g+:
CSS:
.g a {
background: url(logo_g_50x50.png) no-repeat;
}
HTML
<li class="g"><a href="plus.google.com/meeeeee">+1 me on g+</a></li>
and done!
It's easier to read and even easier to maintain for later reuse or additions