You would like to do three things:
- move the site to a new platform (Wordpress)
- add a new content
- change the internal linking structure (presumably navigation)
And you want to preserve your good ranking (of course).
There are few things to assess and you will have to balance lower risk but less sustainable option with higher risk, but more future proof option.
A) Lowest risk, but least sustainable The lowest risk but the least sustainable option is to move the current site to Wordpress, keeping the URLs the same, the site structure the same and internal links and navigation the same. This also means keeping the method on how main navigation operates the same e.g. if you have secondary menu open "on click", do not change it to view the secondary menu "on hover" (or vice versa) as this changes internal link structure.
For this option, you would not need 301 redirects (apart from perhaps home page), so there will be no (estimated 15%) link juice lost owing to redirects. Home page will probably need redirect so that it uses domain root and not index.html.
Once the moved site is re-crawled, and hopefully your rankings remain unchanged, wait a few weeks at least to ensure ranking is stable and then you can work on new content and/or internal links structure as a next step. If changes to internal links structure has adverse effect, you can revert in a hope that previous rankings will return.
B) Medium risk, a bit more sustainable The steps as above, but change URLs to be extensionless (i.e. without .html). Create 301 redirects from old URLs to new URLs. There will be some link juice lost, but from my experience it does not affect rankings much. You will have to make sure that internally you are linking to new extensionless URLs.
Again, you can execute new content and internal navigation changes as next steps once your ranking after the move stabilises.
You will be here in a better position because you have extensionless URLs (on the surface, technology agnostic), but you will put Google through at least two cycles of site changes, once when changing URLs and second time when changing internal linking structure and adding new content.
C) Higher risk, but longer term sustainable This would be what is normally classified as "site redevelopment". You change at the same time URLs, internal linking structure, navigation and add a new content. It is difficult to predict the results, but
if executed technically without any errors, if the structure has improved, if the new content is of a good quality, then *usually* this does not bring long term problems, but it will almost certainly bring
short term ranking fluctuation. How "short" the short term is depends on the size of your current and the new site, i.e. how long it is required for Google to digest changes, process redirects, evaluate new and changed pages and so on.
D) The highest risk The highest risk is site migration where the execution introduced technical errors. For example, Wordpress has the habit of leaking URLs with various parameters that result in duplicate content pages. These will have to be handled by robots or redirects or noindex. Leaking huge number of these at once because of a mistake during a migration can tank the site almost instantaneously.
FEW SUGGESTIONS Whichever route you decide to go, try to make sure of the following:
1) Buy a throw away domain to have as a test site. Block it from Google by either password protecting it or by serving 403 Forbidden to bots (or better, allow only your own IP if you have a static/sticky IP). Least preferable option is to use robots.txt Disallow: / but better than nothing.
2) Decide on the strategy A/B/C above and then install the wordpress on that test domain. Move the content to Wordpress. Change URLs if required or enter permalink URLs to match your current site if not changing URLs. Make sure you are using root-apsolute URLs in your content otherwise your test domain will not truly be test domain. Hence check all content that URLs start with / (and not with http:
//example.com/etc If you are using ../../ URL format, get rid of it and again, use root apsolute URLs.
3) Use the same images/root absolute image URLs on the test domain as you have on the live site. This way image URLs will not change
4) Once test site is finished, use a site crawl tool to crawl your site (see
2013 Favourite SEO Tools [webmasterworld.com] and
Favourite SEO Tools [webmasterworld.com] threads for reviews of useful tools you may want to use for this). Crawl both sites, the current live one and the test domain. Compare the results. If changing URLs, create list of URLs from live site, change the domain name to test site and crawl this list against the test site, ensuring that the redirects are implemented correctly.
When crawling, make sure you crawl with robots.txt honoured as well as with robots.txt ignored, to get the full picture.
5) If there are new URLs/URL patterns to be blocked on Wordpress that you do not have currently blocked on the live site, upload robots.txt on the current site WITH NEW PATTERNS ADDED at least a few days before the actual migration. This is because Google may cache robots.txt for up to 24 hours and putting the new site on the same domain live may result Google seeing pages that it does not know are blocked because it did not re-request robots.txt yet.
6) If you have changed URLs (gone extensionless), create a new sitemap.xml
7) Once you are happy with the site on the test domain, copy the complete content on the live. Pay attention that you have not by mistake copied over test robots.txt and in that way inadvertently blocked the site. Also upload a new sitemap.xml Your .htaccess from test domain will need to be changed slightly to replace domain name from test domain to your domain in .htaccess conditions and rules - be careful of this. Also make sure you remove 403 or password protection from test .htaccess before uploading it to live.
8) CRAWL your site again with a tool as soon as it is live - to make sure the URLs and response codes are as expected. If you have changed URLs, crawl the list of old URLs to make sure they redirect in one step
9) Once you are happy - and if you have changed URLs, go to WMT, perform Fetch as Googebot of the site root and submit the page and all linked pages to index. Perform submitting a new sitemap to Google.
Note: when testing redirects, test both www / non-www URLs from the old domain, to make sure redirect is performed in one step.
Good luck!
