I’m putting this little list here because I always tend to have difficulties to remember what great tool I used half a year ago to do this or that. I probably won’t be updating it too often, but hopefully I won’t forget to update it when I find new useful services 😉
PUCK Free Secondary DNS Service: as its name says, it provides a free secondary DNS server. You usually need that just because you’re required to provide at least 2 DNS servers when registering your domain name, even though on a small side hosted on a single server this kind of redundancy is a bit pointless… With this site a least it won’t cost you.
Pingability: I use it for its great, free DNS analysis service, which checks all your DNS records, on all you DNS servers (primary and secondaries), and reports errors and provides advice on how to optimize some settings. But they also provide, as their name suggests, uptime monitoring (non-free).
Qualys SSL Labs – SSL Server Test: I discovered this one only recently, it’s great to see how well your HTTPS is configured. With this I notably discovered that my server was vulnerable to the BEAST attack (whatever that means…), and was pointed to an easy way to fix it.
SPF record syntax: not a tool yet I’m adding it because it’s a quick and clear guide on how to write a proper SPF record. If you browse the site a bit, you’ll eventually find this page that lists a few SPF record validators.
Woorank: evaluates various points to help you make your site more “SEO-friendly”. Although some points are arguable, it provides a nice overview, with, for each point, advice and links to helpful resources.
Last but not least, the W3C (X)HTML validator and its CSS validator. No need to present them, I guess 🙂 Just it should be mentioned that the HTML 5 validator is still experimental, which seems fair since the standard isn’t finished either after all. And if your page validates, don’t forget to put a validation button 😉