Changing
an individual page is rarely a problem for any site - though you should be careful
with the 'home page' - but radically rebuilding the whole site, involving changes
in domain name, folders, content and filenames, is a very different matter. before
moving domains, or rebuilding on the same doamin, always reread Cool
URIs Don't Change - not only does it encourage you to reconsider, but it gives
valuable lesssons in what to avoid. The risk is that the Search Engines
will see the site as a totally new one, which could cause serious damage to the
'reputation' the site has built up - not to mention individual links to URLs that
will be thrown away. Even if the change is somewhere between the two extremes,
Sick Site Syndrome, for a few months at least, is a real possibility. This
can seriously damage your income. There is no way to guarantee that damage
will not occur; if the changes are radical, then to a large degree, it IS a new
site, and the SEs are right to treat it that way. Here's a few tips to reduce
the risk and minimise the damage. 1. Plan your changes well. Have an outline
of what the final site will be, so you can see the difference. 2. Look at
your statistics; certain pages may be very popular and may have got their own
incoming links; review the plan to preserve important sections if possible; if
not, make a note to use 301 forwarding in those areas, so as to try and preserve
both visitors and 'reputation' 3. Do not start moving anything yet, but
start to build the new sections, with new, additional content where possible. 4.
STOP. Give the new sections time to be 'assimilated' into the SEs knowledge of
your site. It is OK to be adding new material at this point. Building a site map
and submitting it to the SEs would be a good idea. 5. Gradually - NOT ALL
AT ONCE - start moving the material to new sections and new URLs; add those 301s
if necessary. Check navigation as you go; submit a new sitemap after each update. 6.
Be sure you have a useful, reader friendly 404 page. 7. Make the changes
over a period of weeks if you can, so that the 'new' is progressively assimilated
at each spidering. If you can leave some of the site untouched throughout, and
change that next year, that will help. 8. Once the changes are done, check
the navigation again (xenu is your friend); be sure you have a 301 from non-www
to www; check that there are no links to 'index' - all internal 'homepage' links
should go to '/' 9. Start a new program of link building, and get people
to revise old links where you can. 10. Check it all one more time - and
keep your fingers crossed. It can take months for a whole new site to become
assimilated; the time often referred to as the sandbox. New sections or content
on an existing stable site usually settles down and joins the rankings in a matter
of weeks; shorter time for sites that get frequent spidering. That's why
setting up the new site a few months before the move can really help; there's
never a 'guarantee' against the sandbox, but correct 301s, smooth change and stability
appear to be the key points. The only way to avoid duplicate content issues
is not to have duplicate content; specially for interlinked sites (which is risky,
and more so as the number of sites increases). But duplicate content does not
cause a penalty, merely possible supplementary listings, and occasionally (if
identical meta tags etc., delisting. Once the copy becomes unique through later
removal of the dupes, things will self-correct. When changing doamins, there's
no way better than a 301, that's for sure. But there will be some damage; you
will need to start looking to convert as many links as possible to the new site,
especially directories and other key links. And get some new ones. Plus keep adding
(not changing) to the new site. Be sure your navigation is always up to
speed - xenu is your friend. | 
