I've got a project due this week and I've had the javascript 2.8 help site in a seperate window for reference and then without warning--everything is 3.0 in the references and samples!! Can you still get to a 2.8 javascript help site?!?
We only have online help for the current release however you can download the SDK using the ArcGIS API for JavaScript v2.8 SDK link here. Then you'll have a local copy of the 2.8 help.
In Concepts > References > FAQ: To download [older] API and SDK navigate to the ArcGIS API for JavaScript download page and log-in with your ESRI global account.