The latest nightly WebKit (16191) displays unnecessary scrollbars when using position:relative; and overflow:auto;. This does not happen on Firefox and on the Safari included in Mac OS X 10.4.7. A testcase will be attached.
Created attachment 10364 [details] testcase of the bug
This is a regression from r14847 (a fix for bug 9314).
radar 4823102
Created attachment 12558 [details] Don't add relative offsets to {leftmost,rightmost,lowest}Position when not including self
Comment on attachment 12558 [details] Don't add relative offsets to {leftmost,rightmost,lowest}Position when not including self r=me
Landed in r19012.