Redesigning an old site, structure change etc

Question

I have an old site built in 2006, it has around 200 pages and 500 pictures. Every single page is of course indexed as well as images. It is very well ranked for targeted keywords and I receive good amount of SEO traffic (I guess that's due the various campaigns, branding, ppc, etc.)

Problem:
Site has outdated design, pages and images have not so proper names, there are no heading and alt tags, it was built in tables, inline CSS etc.

Goal:
Complete redesign site, use divs, change file names, add proper meta data, alt tags etc.

Question:
How can this affect current SEO positions? I will redirect (301) every single page to the new one, build sitemap, but what to do with images? Do I need to redirect them also? Any other suggestion?

Answer 1

Yes, if URLs are changing - for pages, images, anything - 301 redirect. There is, apparently, a "damping factor" associated with that, at least where Google's concerned, whereby most but not all PageRank etc. is passed to the new address. So if your page URLs are fine (not clear from your question), keep them.

Answer 2

What you thought is right. The better things to keep your benefits (i.e. good ranking, pagerank and so on) is to use a .htaccess and map the old pages with the new ones. Anyway, this could lead a problem. Infact, in my experience, Google could still show in its results the old links for a very long time. I did this action on my website and after almost 1 year a lot of pages are still shown with the old link.