Complex sentence: Netscape is credited with creating JavaScript, the most widely used language for client-side scripting of web pages, as well as developing the Secure Sockets Layer Protocol (SSL) for securing online communication that was used before its successor TLS took over.
Split into simpler sentences: Netscape is credited with creating JavaScript language, the most widely used language for client-side scripting of web pages. The company is also known for developing the SSL which is used for securing online communications that was used before its successor TLS took over.