There is a feature built into all web browsers that allow you to make the text bigger. You can find this under view text size or text zoom. The shortcut on Windows is Ctrl+ or press the ctrl button and roll your mouse button.
There are a couple caveats. Internet Explorer takes the stance that if the web site specifies the text size they can not change this, you need to go into Tools, Internet Options, Accessibility options and ignore the font size. Now IE takes control of the fonts, they do not look proper but you can change the size. Luckily with IE 7 there is another option, to use the zoom function. In fact this is what is used with Ctrl+ or Ctrl mouse scroll. Zoom has the advantage of making all the text and graphics bigger. This is being used by many of the web browsers at this time (Firefox 3 and Opera).