From http://www.w3schools.com (Copyright Refsnes Data)

History of RSS

RSS has been released in many different versions.

The History of RSS

1997 - Dave Winer develops scriptingNews. RSS was born.
1999 - Netscape develops RSS 0.90 (which supported scriptingNews). This was simply XML with an RDF Header.
1999 - Dave Winer at UserLand develops scriptingNews 2.0b1 (This included Netscape's RSS 0.90 features)
1999 - Netscape develops RSS 0.91. In this version they removed the RDF header, but included most features from scriptingNews 2.0b1.
1999 - UserLand gets rid of scriptingNews and uses only RSS 0.91
Netscape stops their RSS development
2000 - UserLand releases the official RSS 0.91 specification
2000 - A group lead by Rael Dornfest at O'Reilly develops RSS 1.0. This format uses RDF and namespaces. This version is often confused as being a new version of 0.91, but this is a completely new format with no ties to RSS 0.91
2000 - Dave Winer at UserLand develops RSS 0.92
2002 - Dave Winer develops RSS 2.0 after leaving Userland
2003 - The official RSS 2.0 specification is released

What are the Differences?

RSS 1.0 is the only version that was developed using the W3C RDF (Resource Description Framework) standard.

The idea behind RDF is to help create a Semantic Web. Read more about RDF and the Semantic Web here. However, this does not matter too much for ordinary users, but by using web standards it will be easier for persons and applications to exchange data.

What RSS Version Should I Use?

RSS 0.91 and RSS 2.0 are easier to understand than RSS 1.0. Our tutorial is based on RSS 2.0.

Is There an RSS Web Standard?

There is no official standard for RSS.

About 50 % of all RSS feeds use RSS 0.91
About 25 % use RSS 1.0
The last 25 % is split between RSS 0.9x versions and RSS 2.0