[SOLVED]............ As usual, five minutes after posting a cry for help on a message board the answer that had been alluding me becomes apparent...
... the guestbook.html was unpublished ( grrrrrrrrr ), I was logged in to the manager in Firefox, so the link worked under Firefox, but not in IE or on the Mac.
[/SOLVED]
I have friendly urls turned on, I have a link to a "Guestbook".
<a href="[~5~]"><img src="blabla.jpg" /></a>
Which works fine in Firefox, but when I try it out in IE ( win ) or Safari the link doesn’t work ,and instead of "MySite/Guestbook.html" I get this in the navigation toolbar...
"MySite/Alias.html?refurl=%2FMySite%2Findex.php%3Fq%3DGuestbook.html&err=1"
( Alias being the alias given to the page with the link )
( asking now before I break anymore things while troubleshooting )