Here's is the current browser support list for IBM Cognos 10 Fix Pack 1 (The latest list is here):
Notice anything odd? It's 2011! These browsers were out of date when IBM Cognos 10 was released. And it's only going to get worse.
IE 8 was released in 2009
Firefox 3.5 was released in 2009 (they are currently on version 6, but it may have changed while I am typing this)
Chrome has never been supported
That might have been fine in 2009, but the landscape of browser use has changed significantly since then:
Source: StatCounter Global Stats - Browser Market Share
So now, when I roll out a new datamart I have to convince users to downgrade their browsers. Aside from usage patterns, I'm already testing my reports in multiple browsers for our user community (my users can install any browser that they want), a greater focus on keeping compatibility with them up to date would likely lead to a more robust non-ie experience. In discussions with my IBM rep they are 'looking into' support for Fire Fox 4 and won't commit to any versions after that. This support model doesn't seem tenable. At the very least I'd like the save icon to work in Fire Fox 4! (it currently does not!) And don't get me started on GoMobile and tablet/mobile browsers.
As many bloggers have noticed already, browser software development is becoming so fluid that it has transcended software versioning altogether. I'm not sure if I totally agree with the voracity of that statement, you'll probably be interested in the version when your 3rd party app stops working, but the point is valid. The current breed of web browsers Chrome, Fire Fox and even IE are continuously updating. Auto updating is now the default behavior. And use of these browsers continues to shift.