1. Using public-key encryption, the sender and recipient of a message do not need to agree on a shared secret key before initiating secure communications. How is this possible? That is, how can the sender, using publicly available information, encode a message that can be decoded only by the intended recipient? 2. List down 20 HTML tags along with their description. 3. List down 5 colors and give their respective names, hex code and RGBA values.(refer this please look more for RGBA value) 4. List down 20 CSS properties along with their definitions and usage. (refer this)