What's the point of valid CSS/HTML?

Question

If I\'ve tested my pages in most major browsers, why would I need to maintain a validated code? I want to use box-shadows and corner radius if they\'re supported in WebKit b

Answer 1

There are sometimes css or html attributes that are marked 'invalid' by some validators, but you shouldn't worry about this. Using box-shadows and rounded corners is no problem at all. Browsers that do not recognize them will simply ignore them, so no trouble there. I'd even encourage you to use those - if too many people would wait using those until they're widely supported, the web's momentum would become much too large.

However, there is a reason for having a valid HTML structure in your document. It isn't hard at all, and it'll save you encounters with inconsistencies in wrongfully-shaped-document-handling across browsers.

I never really understood why we are actually allowed to write structurally invalid HTML. Document readers will most likely barf out PDFs that aren't well-formed, but HTML 5 even seems to have a formal specification for error handling...

Answer 2

• Google prefers it so it is good for SEO.
• It makes your web page more likely to work in browsers you haven't tested.
• It allows you to generate or use your page as an XML document.
• It makes you look more professional (to some developers at least)
• Compliant browsers can render XHTML faster than HTML in quirks mode.
• It points out a bunch of obscure bugs you've probably missed that affect things you probably haven't tested e.g. the codepage or language set of the page.

Answer 3

You should always have valid (X)HTML because there are very few occasions where the benefits of not having valid code outweighs the benefits of not having validated code.

For CSS, however, there is little reason to be as strict. All your CSS should be proper and work as intended, follow best practices and optimize where possible. Other than that, use all the browser specific experimental stuff you want, it won't noticably affect other browsers.

Answer 4

One reason for having valid HTML is for accessibility. Screen reading software for visually impaired users works much better if the HTML on the page is valid.

Answer 5

I'll answer by an analogy. What you are saying is like saying I like building my cars with square tires, it might not be valid everywhere, but it works for me.

If you do not make a product that can be available by a maximum of people, how do you expect your product to be known and used by a maximum of people. By ignoring people that are using IE (which is still the majority of people, by the way) your shooting yourself in the foot. You need to create something that can be used by a vast majority of people while trying to follow the standards for those browsers that do follow them.

Answer 6

"Valid" code isn't so much important as "semantic" code. If there are font tags all over the place and list tags that don't close, it'll be both difficult to maintain and hard to parse with strict and proper xml parsing engines.