The final check to your web page, should be W3C. W3C Conformance tests will ensure that your web pages comply to the W3C conventions for HTML and XHTML. Your web pages positions on the search engines are affected by poor page coding. Basically if your coding is not up to scratch then your competitors are likely to get better page ranking.

W3C Markup Validation Service
W3C Validation Service , this is a must for your web pages, input the URL of each page and check for errors. Ideally there should be none, however in practice there may be one or two particularly if using Front Page.

CSS Validator , if your using cascading style sheets then click on this link to check that your style sheets conform to web standards.

Final  and ongoing SEO Checking Tools
 Link Checker Tool, after you have published your website, check your links regularly with this excellent free tool. Within a couple of minutes every link in your website is checked and a report displayed. For ongoing management of a large site in particular, this tool is worth its weight in Gold. Always use this tool after uploading new or changed pages.

Semantic Data Extractor, ok, you have compiled your title and other meta tags, however do you know how it is going to be displayed in some search engines and other listings, use this free tool and check for yourself.

RSS or ATOM Feed Validator
 Feed Validator, if you have news feeds in RSS or ATOM, then you can check these with this handy tool. The tool can operate on a published web page or you can put direct input into the validator.