Question : SEO - Google SERP for homepage of my site fell back to position 21 - what is the reason?

Hi, here is my site http://tinyurl.com/7tbkef

Suddenly the home page for the site in question fell back to page 3 for the keyword 'warmtepomp' on http://www.google.be/webhp?hl=nl&btnG=Recherche+Google&cr=countryBE
The Google SERP's for other pages on the same site with popular keyword combinations of 'warmtepomp' with relevant searchterms like 'warmtepomp prijs' held their positions like before.  I would like to know what went wrong with the homepage for the single searchterm 'warmtepomp'
I have several other sites that rank really high using the same white hat SEO methods.
Please make sure that you use
1 . the right  google page here : http://www.google.be/webhp?hl=nl&btnG=Recherche+Google&cr=countryBE and
2. the right language 'dutch' and
3. the right country spec belgium (be-nl)

Answer : SEO - Google SERP for homepage of my site fell back to position 21 - what is the reason?

When is the last time you've made any content updates or other changes to the site?  If Google sees a 'dead' web site, they may treat it like one.  Even changing a few words every so often or updating images can go a long way in keeping your site relevant in the eyes of search engines.

Another factor may be your 'expires' meta tag:


From what I've read, this tag is not read by search engines, but why risk it?

Also, look into who is linking to you.  That's the biggest factor in search listings, so if you've lost a few links or the links to you are no longer highly ranked themselves, you may need some fresh PR or partnering to boost your visibility.

Hope this helps.