The Can I Use website compares support of HTML and CSS features across major browsers and discusses any browser issues that come along with that feature.
I can use the information from Can I Use when designing to be aware of browser support of features, be aware of any issues, find feature-specific resources, and test my website on different browsers.
One interesting property is caret-color. This property can be used to change the color of the caret (the blinking line in textboxes). Another interesting property is resize. It allows an element to be resized by the user.
Can I Use gives information on browser support of various CSS and HTML features.