You have a site that's getting on a bit. Your developers are building a new, shinier version and one day the new site goes live and the old one is switched off. You've migrated your site.
With a bit of help, it can all go swimmingly.
However, there are plenty of issues that can affect your traffic and in some cases drastically. Here are two:
1. Page Address Changes
The urls (page addresses) of your new site can be different to those of your current site. The fix is to find out the addresses of your pages and make sure they are redirected successfully.
If this doesn't happen, then it's possible for Google either:
- to forget (de-index) your old urls so people can't find them in Google anymore
- to send search visitors to your error page so they see "PAGE NOT FOUND" and leave (because that gave them a poor visitor experience).
Either way they'll go looking for a competitor. Google will find (and index) your new urls at some point but in the meantime your hard-earned organic search results may suffer a drop.
New site? At the very least you'll want to take the opportunity to check the optimisation (title tags, meta descriptions, page titles, page descriptions) and maybe even re-optimise some or all of your pages.
What could go wrong? The worst case is to not bring the optimisation over to your new site. If this happens your beautiful new site could drop down the rankings, taking your organic traffic (and revenue) with it.
3. What else?
There's a lot more to investigate (this is why we have a mammoth checklist of items to work through). Plus you'll want someone to keep an eye on your Analytics as the migration unfolds.
3.5 Handy Tip
Don't carry out the final step (the DNS changes that point to the new site) on a Friday afternoon. It's risky not to have full support available from all the teams involved. Try to schedule it for Thurs morning at the latest.