The installation instructions say that the versions needed for these files are:SOCKETS.SYS=5.3007, AFOS2.SYS=5.3001, AFINET.SYS=5.3006 or higher
To see what you have, enter the command "INETVER" on the command line.
If you have an MCP version of OS/2, or any version of eCS, you should have the correct TCP/IP levels.
The instructions also say not to use lower versions. I've seen lots of reports that Mozilla does work with earlier versions of TCP/IP (such as the 16bit stack). And others who report that it works, but, they have occasional strange problems. So, if you don't have the latest TCP/IP, it may be worth trying Mozilla. Also, this restriction came in before Mozilla 1.0 was released, so, if you are just thinking of updating a current Mozilla installation, you are probably OK.
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David