The kendo.compatibility.css file fixes problems caused by CSS rules in Site.css - the default stylesheet in the MVC project template. Some of the rules in Site.css have global or high-specificity selectors that break Kendo UI styling. Generally, you don't need this file for real-world applications, which use custom styles more wisely.
We have recently included a similar explanation as a comment inside this file. Changes will take effect in next releases.
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