To correct this problem, make sure your network connectivity is working. Open another TCP/IP application (use ping, telnet, FTP, news, gopher for example) and log in to a remote server to verify your network connectivity. If that works and the IP number of your DNS is correct, Mosaic will work.
If you get DNS errors from your other TCP/IP application, make sure the IP number for the DNS is correct. Typically an Internet access provider will supply you with IP numbers for both a primary and alternate DNS. You should list both DNS servers in case one of the servers goes down for maintenance. Another cause of failed DNS lookup is when the name of the machine you request information from is not listed by the DNS or there is a typo in the address.
Many people try to use other 16-bit winsock software with Windows 95. All 16-bit applications operate in a 16-bit subsystem under Windows 95. Win32 applications like Mosaic apparently are unable to communicate with these winsocks. NCSA recommends you use the native Windows 95 TCP/IP protocol support.