For the latest HTML 5 features, you'll want to use Safari 5, not Safari 4.
Your go-to resource for running applications in Wine is the Wine Application Database (AppDB), which incorporates invaluable test results from outside of the Ubuntu community and should have the most up-to-date information on compatibility.
The most recent test results report success running Safari 5 in Wine 1.3.2, which is available in the WineHQ Repository. Right now there are not any special installation instructions posted. Typically this means you don't have to do any special setup, but you should be open to the possibility that the users posting results for Safari 5 have wrongly assumed that you know to refer back to some part of the Safari 4 installation instructions. If things aren't working as well as reported, try applying the installation instructions for Safari 4.