Accessibility Controls

Here you can customize the appearance of pages of this website for accessibility.
Your choices will be remembered each time you visit (provided you have cookies enabled in your web browser).

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Text Size

Current setting: 0% of default value

Change text size:

1. The dimensions of the page and the main sections of each page on this website are adjusted in proportion to the text size, so that if you choose a text size of 120 (20% larger than the initial value), the page (the central part containing information) will also be 20% wider; and so on.
   
   
2. Just as the text size shown on the screen is a percentage of the default text size (the size to which text returns if you select “Reset”), so also the sizes of the steps, 1% or 10% smaller (minus) or larger (plus) are always percentages of the default text size, not of the current size.
   Mathematicians will appreciate this distinction immediately. For anybody interested but unsure about the exact semantics and arithmetic of percentages, here is one simple example of what this means.
   Suppose that you decide that the default text size is rather too big for you, and you click “−10%”. The font size will be reduced from 100% by 10% to 90%. However, if you click “−10%” again, the amount by which the font size will be reduced is 10% of the original size, that is, from 90% to 80%. A third click will take the size from 80% to 70%. Now, as anyone good at arithmetic will understand, from a value of 80, a 10% drop based on that value is a drop of 8, not of 10, giving a new value of 72. But to keep these controls simple, the step sizes are constant. If you really wanted a text size of 72% here, click -10% three times and then +1% twice. The smaller step of 1% may seem very small, but for some people, using some browser programs and some sizes of computer screen in use nowadays, a 1% change in text size will be useful.

For more information about the accessibility aspects of using browser programs to access other sites on the World Wide Web, see our other page on Accessibility.