[i_feel_great]

Very helpful.

Maybe a mention of using https://validator.w3.org/ would also be helpful to check that all the html is correct and complete.

[EricHolden12]

Oh man, this takes me back.

i remember learning CSS/XHTML and getting your website to pass the validator so you could proudly show the badge on your website was a big deal.

[mro_name]

I am lazy and run html-tidy.org.

[MatthiasPortzel]

I would put “check for spec valid HTML” far down the TODO-list. I’m a perfectionist, so I would run the validator at some point, but I find it’s basically never helpful for identifying usability issues with a website. For a non-technical person setting up a personal site, does it really matter?

[berkes]

Browsers have gotten really good at it, but man, have I wasted hours, missed deadlines because of a stray `<li>item2<li>` and such.

HTML validity and rapid feedback is just as important as the rapid feedback of unit-tests, a type-checker or a even a linter: it shows you mistakes when you make them, rather than later, when you'll merely run into their effects.

[jcynix]

Yes, validation is a good suggestion. And there's http://jigsaw.w3.org/css-validator/ too, both can be linked to from inside a web page via http://validator.w3.org/check/referer and http://jigsaw.w3.org/css-validator/check/referer to ease repeated testing.

[skyfaller]

There's also a ... newer version? at https://validator.w3.org/nu/

I'm not 100% sure what the difference is, but you can see the source code at https://github.com/validator/validator and report any issues.