Avoid large blocks of italic text - this can appear 'wobbly' on screen, and is difficult for many people to read. You don't have to use a large font size on your page. However, ensure that you use relative font sizes in your code, not absolute font sizes. Some browsers can't over-ride absolute font sizes. Don't underline large blocks of text.
Some people find underlined text difficult to read.
In addition, since underlining usually indicates hyperlinked text, it can be confusing for users if it is used where no link exists. Use headings appropriately. Don't use headings simply to increase text size, and don't simply use bold or a larger font size to simulate headings. This will let the user know that the image contains no information and performs no relevant function - they are not left in the position of knowing the image exists but being unsure of what it might contain or do. The linked areas of image maps should always have meaningful ALT text, and text versions of the links should always be provided.