High contrast: This is a way to alter how you view online/computer content. It is an accessibility feature that is built into most computer and allows people with vision impairments or specific learning needs to change the size and colour of fonts and the background for ease of viewing.
For example: You may alter the size of font size, colour and background on Learnzone to suit individual learner needs.
For more information about accessibility visit the Microsoft accessibility webpage: http://www.microsoft.com/enable/