Basically, you don't want to set a width on a box that will have varying input text lengths. But if you don't specify a width the box takes up as much width as it can in a browser window. So your text is left aligned to a centered box that is 100% wide. The solution: Specify a width for your box, but in em units. That way when a user increases their font size, the size of the box will also increase along with the font.