Complex sentence: Microsoft's Internet Explorer 3 was released in that year, featuring some limited support for CSS, and 4 and Netscape 4.x added more, but it was typically incomplete and had many bugs that prevented CSS from being usefully adopted.
Split into simpler sentences: Microsoft's Internet Explorer 3 was released in that year, featuring some limited support for CSS. IE 4 and Netscape 4.x added more support, but it was typically incomplete and had many bugs that prevented CSS from being usefully adopted.