Bold fonts are often calculated fonts based on an algorithm that adds extra pixels around the edge of a 'designed' roman font. When you get the combination of an 'undesigned' font size and the 'bolding' algorithm, that's when things start to get nasty and is, unfortunately, what you have to put up with in web page typography. It's not just the character shapes that suffer, the tracking and kerning goes too. Italic fonts are best avoided. They are completely at odds with the constraints of a square pixel grid and will almost always look awful, but especially so at small sizes.
Many people use graphics for headlines.
These can be created in Photoshop or other graphics packages, saved as GIF files and will generally look better than the indigenous type and give a lot more scope for individuality. They do take longer to download though, and there is the possibility that the user has switched off, or can't display, graphics. It is especially important to make use of the 'ALT' tag for graphics that contain text so that the headline message is not lost altogether. I K E Typographic tricks like letter spacing are a little more difficult to achieve in HTML as it only allows one space between any two characters. You can letter space a word by inserting a discrete space between individual characters, but when it comes to word spacing, you get stuck because you need two or more.