There must be something else wrong in your books, because bold works perfectly fine.
Either of these is correct:
Code:
<p>This is <b>bold text</b>.</p>
<p>This is <strong>bold text</strong>.</p>
or:
Code:
<p>This is <span class="bold">bold text</span>.</p>
with CSS:
Code:
span.bold {
font-weight: bold;
}
How are you testing this?
And where exactly is the bold not showing up?