Hi there @Giyomu, and thanks for sending your code in!
This is not looking too bad at all — you have got most things right. There are a few things to look at, and I’d invite you to look at our marking guide to see what we did: https://github.com/mdn/learning-area/blob/master/html/introduction-to-html/marking-up-a-letter-finished/marking-guide.md
The main things I noticed were:
<div class="sender-column">, you could’ve use an
<address> element in place of the
<div>, to surround the whole lot of the contact details. “address” doesn’t just mean postal address.
For the quote/cite, we went with this:
<p>University of Awesome motto: <q>Be awesome to each other.</q> -- <cite>The memoirs of Bill S Preston, <abbr title="Esquire">Esq</abbr></cite>
The cite attribute should contain a URL to the source of the quote, rather than the name of it, but it’s not very useful because it doesn’t provide a link to the source, or anything. If you have a link to the quote source, doing something like this would be best:
<p>University of Awesome motto: <q>Be awesome to each other.</q> -- <cite><a href="https://www.link-to-the-source.com">The memoirs of Bill S Preston, <abbr title="Esquire">Esq</abbr></a></cite>
Now onto your validation errors — bear in mind that the W3C validator is a useful tool for finding errors, but it isn’t the absolute truth in terms of whether a page is good or not. A lot of code you see online will have validation errors. You should fix as many validation errors as you can, but 100% valid is not always an absolute necessity.
Looking at the errors, it is complaining about finding a closing
</p> at line 52, with no matching opening
<p>. This is because you’ve not closed the
<p> at line 39 when it finishes, then nested your unordered list inside the paragraph, then finally closed it at line 52.
at line 52 will fix that problem.
Then you’ve got similar problems further down - you don’t nest lists inside paragraphs, and you need to make sure all the paragraphs are opened and closely properly.