If the line-break in the word hy­phen­a­tion falls between 'a' and 'tion', then neither a hyphen is displayed nor the letter 'a'. Safari shows: hyphen[break]tion This is the case for every (random) string (a word) where a single char (normally a vowel) is directly preceded and followed by ­
Created attachment 19115 [details] simple html that shows the bug (?) when you change the size of the window.
Confirmed in Webkit r30191
<rdar://problem/5607547> Fixed in <http://trac.webkit.org/projects/webkit/changeset/30644>
*** Bug 19080 has been marked as a duplicate of this bug. ***