Best edit the HTML by hand at this point. You might want to change the <font> tag entered by Illustrator. Try adding a 'style' attribute (eg: <font style="font-family: Arial, Verdana; font-size: 16px;">) or better yet, link to external style sheets (a bit beyond the scope of this forum).
As jimoblak says, you can only use a font if it's available on the end users computer. In the example just given, you can see that you can specify the order of preference for fonts. So if you want to use, say, a font called Interface, but failing that Arial or any sans serif font, you can code it like this: font-family: Interface, Arial, sans-serif;
Likewise with the font-size attribute. By specifying pixels as the unit, it is less likely (but not guaranteed) to break your layout without resorting to graphics. Of course, there are disadvantages to this too, but then, nobody said web design was easy!