And a longer answer:
The only compatibility issues with Publisher 2003 and 2007 webs and IE8 RTW
reported thus far are problems associated with 'grouping'. Any design
elements that are 'grouped' together, which includes the Publisher wizard
built navbars, do not render when you view the web page in IE8 . The fix in
general is to ungroup the elements. There is both a manual fix to these
issues and a Service Patch that has been issued to fix it for Pub 2007.
Reference: Navigation bars and other content is missing from Publisher HTML
output in Internet Explorer 8:
http://support.microsoft.com/kb/969705
A manual method of fixing this grouping issue:
Prior to uploading your pages find all text boxes and other design elements
that are grouped together and ungroup. You can save those changes to your
publication. Then make a copy of your publication by doing a 'File > Save
As' and in this copy go to each page > Edit > Select All > Arrange >
Ungroup. This will ungroup the Publisher built navbar and disconnect it from
the wizard, and the navbars will render correctly in IE8. 'Publish to the
Web' from this copy of your publication. When you want to make further
changes in your web, go back to the original Publisher file, make the
corrections there, save your changes, and again make a copy, ungroup the
navbars and produce new web files for uploading. The advantage of this
workflow is that you will not have to rebuild the navbar if you choose to
add a page to the navbar. If you do not need to add a page, you can leave
the navbar ungrouped and skip the step of saving a copy.
This is also fixed with the Office 2007 SP2: Reference: Description of 2007
Microsoft Office Suite Service Pack 2 (SP2) and of Microsoft Office Language
Pack 2007 SP2:
http://support.microsoft.com/?kbid=953195
The usual caveat also applies. While I would never recommend to anyone that
they not install any security or service patch, when you install service
patches there can be unintended consequences. You might fix one thing only
to break something else. While I have not had any problems on a test
computer there have been other people who have posted about problems opening
Pub 2007 files after installing the Office 2007 SP2.
http://support.microsoft.com/?kbid=953195 lists some of the other known
issues along with some of the things this patch fixes in Office 2007
applications.
If you do have problems after installing SP2: Microsoft Service Pack
Uninstall Tool for the 2007 Microsoft Office suite:
http://support.microsoft.com/kb/954914/en-us
If it were me, I would probably ungroup the navbars manually rather than
install the SP2 for the short term, and wait until MSFT debugs the Office
2007 SP2, rather than risk not being able to open pre-existing Publisher
files. But to each their own...