Double check that the HTML code in your entire website has closed tags and all of the links are functioning properly. Broken links can make it to where the search engines do not index all of your pages properly. In some cases a search robot may decide to stop indexing because of broken links. This is one of the largest problems we find with bad ranking websites.
Most HTML editors have code checking functions to help publish an error free web page.
In the event you should decide to move one of the pages, maintain the original URL intact and have it forward visitors to the new webpage.
Insure that the search engines are able to send their search bots into your site with ease by setting up a robots.txt file. You can control to last detail how search crawl your site by programming it to allow web crawlers to index certain files and folders and block them from other parts of your site.
Avoid reconfiguring your URLS frequently. A simple URL is easier for the search bots to crawl and for people to type. An easy to remember URL is more easily used as a link from another site due to the fact that it is easy for people to remember.