Opinions of seo experts wanted please - advice/possible reasons for decline

All

I'm looking for a few experts in seo to share a few opinions about what has happened to a friends site (it's mostly for a report, so I am looking for "trusted" sources of information backing up these arguments/reasons)

Basically a few months ago a website ranked well for a few competative phrases, (roughly three more, all involving part of the domain name) but now only ranks for two phrases, both being variants of the domain name)

i.e domain is "orangepants.usa", so it ranks on first page for "Orange pants" and "orange pants usa" (that is an example - not related to this)

Since it was ranking well for those phrases basically the below has happened

- website moved onto server where similar websites are hosted (some of which link to the website)

- website has had a new cms installed, resulting in different coding

- titles, description and header text has been altered, as well as the front page content

- some inbound links had been temporaily removed - now re-instated (some articles from 1 website, not many though this that could not be the sole reason?!)

- overall amount of seo work has declined, including article, directory submissions and posting news on the website

If any seo expert could PM or reply here, I;ll give them the link, perhaps they could spot any penalisation at all?

I guess I'm looking for "proof" that on page work is important, as are more factors than simply links to a website?!

any guidance/offerings would be appreciated

 

all of those thing contributed, search engines dont like things changed around a lot

 

thanks for the reply

I agree completley that there are more than one reason, but I'm looking for guidance to find sources of information backing this up?