The programming language developed by Sun Microsystems for building web applications is Java. Introduced in the mid-1990s, Java became popular due to its "write once, run anywhere" capability, enabling developers to create applications that could function on different platforms without requiring modifications. This versatility has made Java a dominant choice for enterprise-level applications and web development. Moreover, its robust security features and extensive libraries allow for the development of dynamic and interactive web applications, contributing to its longstanding relevance in the technology sector.