The oldest versions of Internet Explorer are no longer in use by any majority of users. Web developers will ignore them. Their functionality is outdated.

Version 5.01 (November 1999) Primarily a bug fix for 5.0.
Version 5.0 (March 1999) The first major browser with XML support..
Version 4.0 (October 1997) is used by less than 1% of the Web surfers. It has respectable CSS and DOM support, but no XML support.
Version 3.0 (August 1996). Now used by less than 0.1% of the Web.
Version 2.0 (November 1995). It is too old. Nobody uses it.
Version 1.0 (August 1995). Does anyone remember it?