If you are creating or managing a website there are a number of free tools out there you can use to monitor traffic, check your site for errors and earn money. This is vital for optimising your search engine position and maximising the number of visitors you receive.

Whether you run the site for fun or profit these tools are essential! I use all of these running my site. Some more than others but there is nothing listed here I haven't personally found some value in.

Site Management & Traffic Monitoring

Google Webmaster Tools

Bing Webmaster Tools

Google Analytics

Yahoo Site Explorer

Earning Revenue

Google Adsense

Website Authoring

W3 XHTML/HTML Validator

W3 CSS Validator

Social Networking Features

Google Plus One Button