Search Engine Optimization project & html, css error repairs

I have a website that needs SEO optimization. There are coding errors which need repair and optimum fine tuning, pages to link. For example, categories are listed on the home page. Categories are linked to page 1 & page 2, but not page 3. Inventory growth is now demanding the 3rd page to be linked with pages 1 & 2. My HTML was updated last December using my die-hard Front Page 2003 software. Because of incompatibility issues, I upgraded to Microsoft Expressions Web 4.0. My domain and hosting support is through GoDaddy. The nature of my website involves 20th century militaria antiques. Therefore items listed are all one of a kind. Sold items are edited "sold" and left sold for 30 days. New items are added often, then the website is updated and published. Jim Cheshire at Microsoft found compatibility errors with web browsers which needs addressing again to make sure SEO is in place on all of the major browsers and those browsers are showing my website as it has been designed. MS Expressions 4 is showing coding errors. If there are formatting errors, they need to be repaired. General coding errors need to be looked at. Fine tuning from GoDaddy will be needed to accomplish proper SEO; i.e. keywords, meta-tags, etc. At the bottom of each page is an order button along with a back button. Each of these two buttons need to be duplicated below the category identification text due to the length of the pages. Any formatting suggestions are welcome for a more user friendly website. I know I need a cart and checkout, but am unsure if I can afford that at the moment. Cheshire also found it necessary to use .ftp rather than my HTTPS in order to be able to publish. FrontPage extensions was also necessary in order to be able to publish. I would like the task bar to read https: as it did before. I use a dedicated server with SSL. Security is important for some of my clients. I would like that looked at. I understand there are some upgrades to make Expressions Web 4 work better. Whatever can be done to assure better performance, more user friendly for me when editing and a more user friendly website is of interest. Once again, I may not be able to afford everything I am talking about, so input from the technician is vital.