Google pagespeed insights
As most of you already know, nowadays mobile browsing has surpassed desktop browsing. This is why the loading speed of your website is an extremely important factor of its general quality.
Google has created a tool that allows website owners to check how fast their websites are to load. There are countless sites which can help you to check your site speed and hence fix issues, such as Pingdom. The reason I prefer to use Google’s is because the search engine considers website speed an important factor of quality, and the speed of your websites affects your rankings.
→ Visit Google PageSpeed Insights
W3C validator
While probably not a super important factor of quality anymore, valid code is a sign of a web developer who has an attention to detail and pride in their work.
Invalid code doesn’t affect your SEO, and most of the time, it won’t make your user experience worse. But it has to have a balance: sure, 100% valid HTML isn’t as important and “hyped” that it was in 2009. But it still matters.
The reference tool for checking the quality of your HTML markup and CSS code is the good old W3C validator. And if you haven’t checked a document for years, you’ll probably be interested to hear that they have created a new tool called “Nu HTML”.
→ Visit W3C Validator
ScreenFly
If you own a website, you want it to look good. But does it look good on other devices? As you can’t own 5 smartphones, 10 laptops and 5 desktop displays, the best way to check how your website looks on multiples devices and resolutions is to use a tool which allows you to visualize an url under different resolutions.
As often, there’s a lot of different tools competing. My favorite is by far ScreenFly, for its modern and easy-to-use interface as well as its predefined presets
→ Visit ScreenFly
Achecker
According to W3C, “Web accessibility means that people with disabilities can use the Web. More specifically, Web accessibility means that people with disabilities can perceive, understand, navigate, and interact with the Web, and that they can contribute to the Web.” So, in terms of ethics, it’s definitely an important aspect of a quality website.
AChecker is an online tool that checks HTML pages for conformance with accessibility standards to ensure the content can be accessed by everyone.
→ Visit AChecker
WebPagetest
Here’s a free online tool which allows you to run a free website speed test from multiple locations around the globe using real browsers (IE and Chrome) and at real consumer connection speeds.
You can run simple tests or perform advanced testing including multi-step transactions, video capture, content blocking and much more. Your results will provide rich diagnostic information including resource loading waterfall charts, Page Speed optimization checks and suggestions for improvements.
→ Visit WebPageTest