Lotus Notes 6.x:
navigator.appName => "Lotus Notes"

Lotus Notes 7.x:
navigator.appName => "IBM Lotus Notes"

If you use JavaScript in Lotus Notes to distinguish bt. Notes Client and Browser this code will not work anymore.

e.g.
navigator.appName != "Lotus Notes" => always true in Notes 7.x

Possible Solution:
navigator.appName.indexOf("Notes") == -1