After reading the CSS2 reference at www.w3schools.com, there doesn't seem to be a way to write text vertically on the screen. You can set the text to be displayed left to right, or right to left, though.
If there is a font out there that displays letters vertically, or at least rotated 90 degrees, that would work, but then you'd have to get into downloadable fonts.
Your best bet is to create that text in a graphics program like Photoshop or Paint Shop Pro. You may even be able to do text vertically in Flash.