Javascript differences are much more subtle. . . Those writing Javascript often make the mistake of using much too late a code version for the installed base of browsers. They then fail to test on any other platform other than the one they regularly use. Currently the world standard is 4.0 browsers even though there are much newer browsers on the market. However, I still test on my old 486 running Win3.1 and Netscape 3.2 using a 640x480 monitor.
Progress waits for no one.