Do css errors and missing files affect PageSpeed ​​Insights?

Question

Google

We asked the site to look at the subject of passing the test and I don’t know from which side to approach. I checked it on validators - there are a lot of errors, there are missing files, but how to find those 20% of the impact - which will shoot at 80%

Answer 1

CSS, of course, has an effect - this is page rendering, whatever one may say: Google itself recommends compression, using 1 file and asynchronous loading, if there are really a large number of styles, and even scripts to catch up.
Files too, because the server spends time on something that is not originally there.
At the expense of the rule 20 - 80 - this, of course, is good, but it's better to do everything step by step and that's it, because in practice there is no 20%, cat. less than 80% is needed, especially when it comes to loading 2.5-3 seconds or more.
In addition, valid CSS is always small, but a plus in SEO, and missing files are a huge hole in it.