Contrast is important when designing a web page for many reasons. One of the most important reasons is because if you don't have contrast, you won't be able to read what is written on the page. Your eyes will have to strain really hard or it just simply won't be possible to read at all. Another really important reason is that contrast makes the web page look visually appealing. Whereas, if you don't have contrast it is all kind of jumbled together. As you can see there is a plethora of reasons contrast is important.
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