Note: if you want a useful HTML playground for sharing your code with others, both jsfiddle and CodePen are good options. If you want your browser to refresh its content on save, I recommend LiveReload. Prepros is by far the best tool for using LiveReload that I've found for Windows, and I've heard great things about CodeKit for Mac.
Input HTML in the top textarea, and CSS in the bottom one. Link to Project.