Check spelling and grammar. Look at word variation, consistency and writing style. Are you using bulleted lists? Are you using the right tone? Is your capitalisation and punctuation in order? Also make sure you're using the H1-H6 tags correctly and all hidden copy (ALT text, Title tags, text in Javascript functions, etc) is all good.

Are images appearing and embedded video working? Optimise images for fast loading times using a compression tool (TinyPNG / iImageOptm) and make sure the logo is consistent and there's a favicon appearing.

Check all links are working, internal and external. Test headers, footers, navigation, body, mailto, RSS feeds, etc. Use a link test tool to speed up the process.

Ensure no test content such as dummy text or images are left on the live production site. Also check for hard-coded links to staging/demo/fake sites now go to their intended location.

Test contact forms, the emailed content from those forms (and reply to it), anti-spam email address links and captcha, email newsletter signups, 404s, search, blog comments, shopping carts, login, registration, social sharing buttons, call to actions etc. Anything that functions, test it. If there are any important pages, do a print test.

Test across various browsers and viewport sizes using browser and responsive testing. Don't forget the viewport Meta Tag and test on your real mobile and tablet devices. You can also use Google's mobile friendly test. Also, optimise for high resolution Retina displays by using SVG, icon fonts and HiDPI graphics.

Add page titles and meta description tags for important pages. Make sure these make sense to humans and have keywords in them. Also ensure the URLs are search engine and user friendly.

Minify and compress any static (JavaScript/HTML/CSS) files. Check and implement caching where necessary and, if slow, check total page size/download time. Google Page Speed, Yahoo YSlow and Peek will help give you insight on what needs to be done to improve site performance.

Install Google Analytics or Clicky on every page. Setup funnels, goals and, if using Google Analytics, link up your Webmaster and Analytics accounts.

Create a sitemap.xml file and submit it to Google Webmaster Tools or Yahoo or Bing. Check for canonical domain issues (link variations like http://yoursite.com, http://www.yoursite.com, http://www.yoursite.com/index.html, and https:// variations). You can set the preferred domain in your DNS settings and also Google Webmaster Tools.

Set a backup schedule and method, make sure any protected pages are "protected", use a robots.txt and .htaccess file where necessary. If you have an SSL configured, make sure it is working and no mixed-content warnings (whynopadlock.com). Store safely any database and FTP or other server connection passwords and if necessary setup domain or server uptime monitoring.

Submit to social networks, feedburner, newsletter list, forums, aggregator sites, press release, friends, the client, etc. It's live, you've made it. Well done. But don't rest just yet. Make sure you keep updating the site and keeping an eye on it. This is only the beginning!