what is validation?


The W3C or World Wide Web Consortium provide on-line validation  tools, on their web site which anyone can use for FREE  and you can validate  as many documents as you need to.
There are tools to validate  html – xhtml  documents as well as CSS  stylesheets  and other types of documents published on the web.
There is also a tool to check anchors  (hyperlinks) in html – xhtml  documents to find broken links.
The validation  tool checks to see if a document is well formed  and that the syntax follows the specification for the version of html – xhtml  used in the document.

I have taken the following text from the W3C web site and reworded and condensed it. The first part about validation is from a document written by Nick Kew and the rest of the text, is from from the validationHelp & FAQ’s on the W3c site.

What is Validation?

Validation is a process to check documents against a Formal Standard, such as the standards that are determined and published by the W3C, for html and xml derived web document types, and also those published by the wml the wap forum, ect.
It can be likened to spell checking and proof reading for errors in grammar and syntax, but it is much more precise and reliable than these processes. This is because it is dealing with very precisely-specified machine languages.
Unlike the very nebulously-defined human natural language that we all use everyday in the process of living our lives.
In the same way that text in our natural language can contain spelling or grammatical errors, documents using html or other Markup Languages can contain errors for various reasons.
The actual process of verifying if a document follows the rules for the language(s) that it uses is called Validation, and the tool that is used for this purpose is called a Validator.
When a document has been successfully proccessed it is then Valid.
Author:Nick Kew

Why even bother with Validation?

There are many reasons why you should Validate your documents, and just as many arguments against bothering to validate documents.
Basically it just means that the document follows the rules and conforms to the standards that have been established.
The fact a web page is Valid is not a form of Quality Control and does not automatically mean that the web page is "Quality Approved" at all.
The actual Validity of a web page is only one of the quality criteria for a web page, and there are many others too, that go into making a good quality web page.
A Valid web page is not necessarily a good web page, but an invalid web page has very little chance of being a good web page.
So because a web page/document is Validated it does not mean it is a good page/document, or that the W3c assesses that it is a good page/document either.
What it does mean is that a Tool has processed the document/page and found it to comply with a specific set of "rules" no more,no less.
So the icon is not to be taken as a W3C seal of quality...

Also Validity and Conformance are not the same, because they are different concepts Markup languages are defined in Technical Specifiactions, and these generally include a formal Grammar.
So a document is Valid when it has been written correctly and also in accordance of the Formal Grammar.
Whereas Conformance relates to the actual Specification .
These two might be equivalent, but in a lot of cases the conformance required cannot be expressed in the Grammar, so this makes Validity only a part of the Conformance.
The actual Markup Validator is a FREE tool and service, and it acts as I have described above like a Spell Checker, and checks the syntax of web documents written in formats such as (X)html.
The validator actually compares your html document with the defined syntax and reports any discrepancies that it discovers in the document, and reports the error in a report.
You can then use the error report and correct any errors in your syntax ect.
The Validator tool is maintained by the W3C staff and seems to be a product of much collaboration.

The most important and also salient reason for Validating html documents is that a browser will accept an html document and try to display the web page, even if the html is not Legal.
This usually means that the browser will try and make an educated guess at how, the author actually intended the page to be displayed.
Unfortunately the problem here is that different browsers will make different guess's, about the same yet illegal constuct.
Much worse can happen, if the html is totally pathalogical, then the browser could become totally confused and produces a mangled mess or worse still it could cause the browser to crash.
This can also happen with different versions of the same browser as well as different browser's, so a page may look totally different in an old browser, compared with the same page displayed in a newer version of the same browser.
Source: W3C web site


It definitely makes sense to Validate all your html – xhtml and css documents then you can be sure that they will have a good chance of working in every browser in the manner you intended.
This will make your web pages more accessible to your target audience no matter what browser they have installed on their PC's.
All things considered it is well worth the effort, even for a little rinky dink web site like this.
Especially today with issues about accessibility, it has cost some big web sites millions because people with disabilities, are not able to access their web site properly.

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