The site looks fine except the few validation issues. Using some validation tools could remedy those issues. The few tools that could be the most beneficial in my opinion are these.

The MarkUp Validator - Also known as the HTML validator, it helps check Web documents in formats like HTML and XHTML, SVG or MathML.
The Link Checker - It checks anchors (hyperlinks) in a HTML/XHTML document or full Web sites and is useful to find broken links.
The CSS Validator - It validates CSS stylesheets or documents that use CSS stylesheets.

Also note that many websites are also becoming more compatible for mobile devices because of their popularity. If one does not care if one on a phone can view your site, then you should not be concerned with the layout.

It may also be helpful to use https://browsershots.org/ to see how your webpages look when viewed with other browsers.

The site does look nice even from a WYSIWYG web based editor.