Every browser has slightly different default font size settings for the <h>eadline elements, which also affects how small, medium, and large sizes are rendered. In addition, the user's settings will also have an impact. But these are all under your control through your stylesheet. You can allow the default settings to prevail or override them as you choose and as your design dictates. Many tutorials recommend using percentages in order to allow the user's preferences to take precedence, but you'll sometimes need to specify an exact font size when you're working in a limited area of a web page. These are things you'll have to balance when creating websites. It is, as they say, an art, not a science. Good luck!