CSS:

border-radius: [px] rounds corners
border:
div.container { height: 60px; width: 60px; border: 3px solid blue; border-radius: 50%; } create a circle
Reset all values: * { margin: 0; padding: 0; }
display: none hides an element entirely, while visibility: none leaves the space for the element visible.
To make padding and border count on the inside of an element, use *{ box-sizing: border-box; }
Changing highlight selection colour: /*** Works on common browsers ***/ ::selection { background-color: #352e7e; color: #fff; } /*** Mozilla based browsers ***/ ::-moz-selection { background-color: #352e7e; color: #fff; } /***For Other Browsers ***/ ::-o-selection { background-color: #352e7e; color: #fff; } ::-ms-selection { background-color: #352e7e; color: #fff; } /*** For Webkit ***/ ::-webkit-selection { background-color: #352e7e; color: #fff; }