Ahrefs Website Authority Checker is a brilliant tool that analyzes the relative strength of a given domain name, by determining how authoritative the website is, based on a count of the number and quality of inbound vs outbound links. Sites that rank high on this 100-point scale tend to perform better in search engine ranking pages than sites with lower scores.

Doctor HTML allows you to carry out a detailed analysis of your HTML coding for a single page. The doctor checks even complex features such as table structure, forms, image syntax and document structure, which can help to ensure that your page is seen correctly in a variety of browsers, while also working out small bugs.

Free Webmaster Tools - as the name suggests, this site provides web developers and digital publishers with access to a range of handy, free web tools. These will make your life so much easier. Everything from whois searches, to RGB/HEX conversions, image resizing, HTML minimising, URL encryption and QR code generation can be performed from this site - quickly, easily and with no need to register. Bookmark this one for regular use.

LinkPopularity.com communicates with the ALtaVista, Infoseek and HotBot search robots to determine just how many pages around the Web link to yours. Obviously, the more links you have pointing to your site is generally proportional to the amount of traffic that you will receive. Remote links are also important for improving your placement on many of the newer search engines, which rate pages by relavance and popularity as well as content.

NetMechanic has replaced Web Site Garage as the best free online maintenance tool for webmasters. This mechanic presents webmasters with the opportunity to scan their entire site for broken links, bloated graphics, rough HTML coding, spelling errors, browser compatibility issues and more. A great service.

SiteOwner is a service provided by LinkExchange and the Microsoft Network. As you may expect, with this knowledge, it is feature-packed and very popular. A number of individual services are provided on the site, including single page tune-ups, search engine submission, popularity checks, a meta tag builder and even a scaled-down version of the PositionAgent software, which tracks your site's current search engine rank.

Weblint is a downloadable application that scans your HTML code for errors or redundancy, thus enabling you to add stablility to your site, while reducing its loading time.