Redesigned site often dropped out of Google for about 2-6 months if you redesigned poorly. The following is a simple guide to redesign your site.
- Google likes stable pages. Keep as original URLS and page name as you can. Keep a backup up your old site that you can re-load if the new one failed in rankings.
- If you're planning on doing an update, with only visual appeal and internal linking. Don't change the directory structure, unless you feel you have to.
- If you change your directory structure, be sure to back-up the whole site first, make your changes, then completely delete the old directories. It is not good of leaving a few behind, which also hurt your rankings. Google was trying to follow links that were'nt there. Thus, to them, it looked like my your was all busted up.
- Benefitial to your users.
- If the "constant redesign" you are doing includes keywords, it will hurt you.will undoubtedly have an adverse affect on your rankings. (particularly for ranking purposes)
- Redesign your page, make sure it is exactly the way you want it before uploading and then leave it alone. Redeign pages just for spelling errors is no adverse affect, but correct a spelling error for a keyword or rewrite a sentence which includes a keyword, it will hurt you.
- Leaving orphaned pages on your site will hurt you way more than removing them! This is something Google really hates. They are considered the same as a doorway page.
- Use 301 redirects to point old pages to new pages if you change the page file names.
- Static site to another static site: keep URLs
- Static to dynamic: difficult to keep URLs, so use 301 redirects
- Dynamic to dynamic, e.g. moving to a different CMS: if you can't keep the urls (which is likely) you will have to use redirects. While you're at it: Try to virtualize your URLs completely (see below).
- If you can't keep the URL and are not able to use redirects, try to get as many inbound links updated as possible. You might also want to consider keeping the old site running and doing the redesign on a completely new site.
Tweaking the layout of a site should always be done with cleaner code as a goal. If the code gets messier your rankings may drop slightly. If the you are using a table based layout, make sure that the text appears in the code in a logical sequence without it being interrupted by too much layout code.
Timing: As a rule of thumb do everything at once. Don't take the old site down and put the new one up a couple days later and then setup the redirects. Instead, do your homework and switch within minutes. Anything else is going to confuse the bots.
URL virtualizing: Some CMSs come with a feature called Pretty URLs. It means that your URLs look like /widgets/blue/new, /widgets/red/used and so on instead of products.asp?catalog_id=2&product_id=5. Most of the time this is achieved by rewriting URLs before they reach the CMS. But even if the technology you're using for your dynamic site does not support pretty URLs you can try to use Apache's mod_rewrite for that. Once you have virtualized, i.e. prettyfied your URLs it will be much easier to change the underlying technology.
Never use absolute URLs. Try to use path-relative or at least domain-relative urls. For example, when you're redesigning a static site that uses absolute URLs, the new design should have relative URLs instead. It is possible to move from absolute URLs to relative URLs without affecting the search engines. The bots know very well how to handle relative URLs these days.