How important is it really to validate codes by W3C?

Question

I understand that validating code can be important and mainly help those who are starting to correct errors and be more informed about obsolete elements in current language versions.

But how much should I care about validating mine HTML and CSS, for example, my code HTML gave a warning that I am using an iframe that has a frameborder attribute and it is obsolete, but this part of the code is actually a Faceboook plugin and anything I change in this part of the code it stops working (I am not in favor of using these social networking plugins but it was client’s requirement).

This was just an example already happened similar things to libraries or frameworks that I tried to use, or even browser hacks that I needed to use to fix CSS in some browsers, and of course hacks are accused as errors in validation.

I currently use this W3C validation only to correct simple errors that I missed, and I don’t try to fulfill 100% of what they indicate.

So I wanted to know, as far as it’s worth to strive to have your code validated 100% by W3C, I mean time and give up elements that you use but that you didn’t develop. Also, is there any real benefit to having the validation or is it simply a fix that allows you to go around saying that your code is good because the W3C said it is?

NOTE: I am not defending completely crazy codes and bad deeds full of mistakes and etc.

Answer 1

Do you need it? whether you are a web developer or a web designer this tool will be a powerful ally. It is not only capable of compare a stylesheet with the CSS specifications, pointing out errors, misspellings, or improper use of CSS, but also will alert you to potential risks to usability.

Source: https://jigsaw.w3.org/css-validator/about.html.pt-BR

The validation service is a tool, so it is up to those who are developing to evaluate whether it is worth making certain changes to stay in accordance with the standards of w3c, it is always good to search for the most correct code possible, but as the example you reported, There was no way the client requested something and you have to comply, is it worth explaining to the customer what is happening? Will the customer want to wait this long? Or bear the costs? Will this generate future problems? All this should be taken into account at the time of evaluation.

And as written on the link above:

It’s just a valuable and reliable tool, except that, being a software-based tool, it is subject to bugs and inaccuracies & legacy bugs and inaccuracies

In other words, it is a great tool, it will show many errors automatically, but it will not be able to discern the domain, it is up to the developer to assess whether or not to make a certain change.