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[2]W3C [3]CSS Validation Service

   Check Cascading Style Sheets (CSS) and (X)HTML documents with style sheets

About the CSS Validator

Table of contents

    1. About this Service
         1. [4]What is this? Do I need it?
         2. [5]The explanation above is incomprehensible! Help!
         3. [6]So, this is the authority on what is correct CSS and what isn't?
         4. [7]What does "Valid CSS" mean? Which version of CSS does this validator
            use?
         5. [8]How much does it cost?
         6. [9]Who wrote this tool? Who maintains it?
         7. [10]How do I contact the authors? Report a bug?
         8. [11]Can I help?
    2. Developers' corner
         1. [12]What is the CSS Validator written in? Is the source available
            somewhere?
         2. [13]Can I install and run the CSS Validator myself?
         3. [14]Can I build an application upon this validator? Is there an API?

About this Service

What is this? Do I need it?

   The W3C CSS Validation Service is a free software created by the W3C to help Web
   designers and Web developers check Cascading Style Sheets (CSS). It can be used
   on this [15]free service on the web, or downloaded and used either as a java
   program, or as a java servlet on a Web server.

   Do you need it? If you are a Web developer or a Web designer, this tool will be
   an invaluable ally. Not only will it compare your style sheets to the CSS
   specifications, helping you find errors, typos, or incorrect uses of CSS, it will
   also tell you when your CSS poses some risks in terms of usability.

The explanation above is incomprehensible! Help!

   Most documents on the Web are written in a computer language called HTML. This
   language can be used to create pages with structured information, links, and
   multimedia objects. For color, text, and layout, HTML uses a styling language
   called CSS, short for "Cascading Style Sheets". What this tool does is help
   people authoring CSS check, and fix if necessary, their CSS Style Sheets.

So, this is the authority on what is correct CSS and what isn't?

   No. It is a helpful and reliable tool, but a software tool, and like every
   software, it has some [16]bugs and issues (and [17]legacy bugs). The actual
   reference on Cascading Style Sheets are the [18]CSS Specifications.

What does "Valid CSS" mean? Which version of CSS does this validator use?

   According to the [19]CSS 2.1 Specification: "The validity of a style sheet
   depends on the level of CSS used for the style sheet. [...] valid CSS 2.1 style
   sheet must be written according to the grammar of CSS 2.1. Furthermore, it must
   contain only at-rules, property names, and property values defined in this
   specification".

   By default, this validator checks style sheets against the grammar, properties
   and values defined in the [20]CSS 2.1 specification, but other CSS profiles can
   be checked against by using the options.

   CSS is an evolving language, and it is considered by many that "CSS" is a single
   grammar (the one defined in the latest specification) with a number of properties
   and acceptable values defined in various profiles.In a future version of this
   validator, the default behavior may be to check style sheets against that latest
   "CSS grammar" and the cloud of all standardized CSS properties and values.

How much does it cost?

   Nothing. The service is free. The source is [21]open and you are free to download
   it, use it, modify it, distribute it, and [22]more. If you really like it, you
   are welcome to [23]join the project or donate to W3C via the [24]W3C supporters
   program, but nobody forces you to.

Who wrote this tool? Who maintains it?

   W3C maintains and hosts the tool, thanks to the work and contributions by W3C
   staff, volunteer developers and translators. See the [25]credits and
   acknowledgments page for details. [26]You too can help.

Can I help?

   Of course. If you are a java programmer, you can help the CSS Validator project
   by checking out the [27]code, adopting and fixing [28]bugs & [29]legacy bugs, or
   helping build new features.

   But you do not need to be a coder to help build and maintain this tool: you can
   also help improve the documentation, participate in translating the validator in
   your language, or subscribe to the [30]mailing-list and discuss about the tool or
   help other users.

Any other question?

   If you have any question regarding CSS or the CSS validator, check out the
   available [31]mailing-lists and forums. But before that, make sure that your
   question or comment is not covered already by the [32]CSS Validator FAQ document.

Developers' corner

What is the CSS Validator written in? Is the source available somewhere?

   The W3C CSS validator is written using the java language, and yes, its source is
   available, using Git: you can [33]browse the code online or follow the
   instructions there to download the whole source tree. For a quick overview of the
   classes used in the CSS Validator code, check out the [34]README file.

Can I install and run the CSS Validator myself?

   It is possible to download and install the CSS validator, and to run it either
   from the command line, or as a servlet in a Web server. Read the [35]instructions
   for installation and use.

Can I build an application upon this validator? Is there an API?

   Yes, and [36]yes. The CSS Validator has a (RESTful) [37]SOAP interface which
   should make it reasonably easy to build applications (Web or otherwise) upon it.
   Good manners and respectful usage of shared resources are of course customary:
   make sure your applications sleep() between calls to the validator, or install
   and run your own instance of the validator.

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References

   1. http://jigsaw.w3.org/css-validator/
   2. http://www.w3.org/
   3. http://jigsaw.w3.org/css-validator/
   4. https://jigsaw.w3.org/css-validator/about.html#what
   5. https://jigsaw.w3.org/css-validator/about.html#help
   6. https://jigsaw.w3.org/css-validator/about.html#reference
   7. https://jigsaw.w3.org/css-validator/about.html#validCSS
   8. https://jigsaw.w3.org/css-validator/about.html#free
   9. https://jigsaw.w3.org/css-validator/about.html#who
  10. https://jigsaw.w3.org/css-validator/about.html#contact
  11. https://jigsaw.w3.org/css-validator/about.html#participate
  12. https://jigsaw.w3.org/css-validator/about.html#code
  13. https://jigsaw.w3.org/css-validator/about.html#install
  14. https://jigsaw.w3.org/css-validator/about.html#api
  15. http://jigsaw.w3.org/css-validator/
  16. https://github.com/w3c/css-validator/issues
  17. http://www.w3.org/Bugs/Public/buglist.cgi?product=CSSValidator
  18. http://www.w3.org/Style/CSS/#specs
  19. http://www.w3.org/TR/CSS21/conform.html#valid-style-sheet
  20. http://www.w3.org/TR/CSS21/
  21. http://jigsaw.w3.org/css-validator/DOWNLOAD.html
  22. http://www.w3.org/Consortium/Legal/copyright-software
  23. https://jigsaw.w3.org/css-validator/about.html#participate
  24. http://www.w3.org/Consortium/sup
  25. http://jigsaw.w3.org/css-validator/thanks.html
  26. https://jigsaw.w3.org/css-validator/about.html#participate
  27. https://jigsaw.w3.org/css-validator/about.html#code
  28. https://github.com/w3c/css-validator/issues
  29. http://www.w3.org/Bugs/Public/buglist.cgi?product=CSSValidator
  30. http://lists.w3.org/Archives/Public/www-validator-css/
  31. http://jigsaw.w3.org/css-validator/Email
  32. http://www.websitedev.de/css/validator-faq
  33. https://github.com/w3c/css-validator
  34. http://jigsaw.w3.org/css-validator/README.html
  35. http://jigsaw.w3.org/css-validator/RUN.html
  36. http://jigsaw.w3.org/css-validator/api.html
  37. http://jigsaw.w3.org/css-validator/api.html
  38. http://jigsaw.w3.org/css-validator/
  39. http://jigsaw.w3.org/css-validator/documentation.html
  40. http://jigsaw.w3.org/css-validator/DOWNLOAD.html
  41. http://jigsaw.w3.org/css-validator/Email.html
  42. http://jigsaw.w3.org/css-validator/thanks.html
  43. http://jigsaw.w3.org/css-validator/about.html.bg
  44. http://jigsaw.w3.org/css-validator/about.html.de
  45. http://jigsaw.w3.org/css-validator/about.html.en
  46. http://jigsaw.w3.org/css-validator/about.html.es
  47. http://jigsaw.w3.org/css-validator/about.html.fr
  48. http://jigsaw.w3.org/css-validator/about.html.ko
  49. http://jigsaw.w3.org/css-validator/about.html.it
  50. http://jigsaw.w3.org/css-validator/about.html.nl
  51. http://jigsaw.w3.org/css-validator/about.html.ja
  52. http://jigsaw.w3.org/css-validator/about.html.pl-PL
  53. http://jigsaw.w3.org/css-validator/about.html.pt-BR
  54. http://jigsaw.w3.org/css-validator/about.html.ru
  55. http://jigsaw.w3.org/css-validator/about.html.sv
  56. http://jigsaw.w3.org/css-validator/about.html.zh-cn
  57. http://www.w3.org/QA/
  58. http://www.w3.org/Style/CSS/learning
  59. http://www.w3.org/QA/Tools/Donate
  60. http://www.w3.org/Consortium/Legal/ipr-notice#Copyright
  61. http://www.w3.org/
  62. http://www.csail.mit.edu/
  63. http://www.ercim.eu/
  64. http://www.keio.ac.jp/
  65. http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer
  66. http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks
  67. http://www.w3.org/Consortium/Legal/copyright-documents
  68. http://www.w3.org/Consortium/Legal/copyright-software
  69. http://www.w3.org/Consortium/Legal/privacy-statement#Public
  70. http://www.w3.org/Consortium/Legal/privacy-statement#Members