On the button bar, click on the 'B' button for bold, or the 'I' button for italic. If you change your mind, pressing the 'B' or 'I' button again will undo the formatting. There is no button on the toolbar for underlining text. You can undo the formatting by repeating this process over selected text. You can also format text with hot key combinations that are used in Windows.
People usually associate underlined text with live hyperlinks to other Web pages.
For this reason, it is best to use underlining sparingly for other purposes, as this can create confusion for those visiting your page. Choose a different font or type size. Use the mouse to highlight the text you are interested in. For maximum control over how your pages look, use only the most universal fonts such as Times New Roman, Arial, and Courier. While you may use any font installed on your computer, people viewing your page may not have the same fonts on their computers.