Building websites that are accessible to all types of users can be a rather tricky process. Not only do you have to worry about browser/machine types, screen-readers, and a plethora of other website ‘clients’, but also possible visual impairments, such as colour blindness.
One fun, and potentially very useful tool is Vischeck, which gives a simulation (as in the image above) of how your website might be viewed under different types of colour vision. Personally I’ve been finding this helpful in finding out whether text is always visible over coloured backgrounds under these conditions. It seems that (far more than I’d realised!) texts merge into backgrounds and just can’t be seen – so the issue of accessibility once again comes as an important factor in the design of a page.