It depends on what you mean by “quality”. The conventional definition of “quality” in the IT industry refers to error-free code. So using the conventional definition it would be any page that validates without error.
There are tools available for Quality Assurance testing:
The W3C QA Toolbox – Validators, checkers and other tools for Webmasters and Web Developers
When it comes to quality content, we could test for spelling and grammatical errors as a Quality Control method.
Here’s an online tool that can help with that:
Grammar Check – Free Online Grammar Checker
Hint: Try running the text from your OP to see an example of how it works.
And for SEO quality compliance we can use Google content quality guidelines:
Webmaster Guidelines – Webmaster Tools Help
Of course, there are many more specific quality tests that you can do for quality assurance in regards to other features of your site:
Techniques for Web Content Accessibility Guidelines 1.0
Welcome to the HiSoftware Cynthia Says Portal
Site-Perf.com – Know all about your site performance
IDI Web Accessibility Checker : Web Accessibility Checker
Web Page Analyzer – free website optimization tool website speed test check website performance report from web site optimization
You can view quality as subjective, however, I don’t think Google views quality as a totally subjective term.
You can set up and measure quality standards. For example, misspelled words and poor grammar can easily be detected. The lack of headings, inadequate spacing in layouts, and certain poorly laid out designs can easily be detected. The lack of contact details, terms, and privacy policy, are also easy to detect.
For years anti-spam algorithms have used linguistic analysis to detect spam and Google has studied similar techniques for detecting low-quality web content. There are a plethora of linguistic rules that could be used to score your content quality.
I have recently noticed significant changes in rankings by making a few stylistic changes of the same content. This was not noticed before the Panda series of updates.
I believe you guys are confusing the term “quality” with “value” or “usefulness”. Those are different words with different meanings. “Quality” implies freedom from error, defect or meeting a standard, not “value” or “usefulness”. I am speaking in context here, the context of search engine listings.
