Validator - necessity of use and practical advice{councils}.

The HTML-standard unequivocally defines{determines} the basic structure of the Web-document. Language HTML is a subset of language of the description of documents SGML (Structured Generalized Markup Language), thus, the html-document is the text document consisting of html-codes and the body text of the document. The WEB-browser is necessary for viewing this document - the special program for interpretation and correct display of page on the screen.

What is standard HTML?

* HTML has been originally developed Tim Berners-Lee and populjarizovan by browser Mosaic developed NCSA. During 90kh he has literally blossomed in connection with rapid development Web. There was time when webs - developers have been compelled to use the html-standard 2.0 (has been developed under aegis Internet Engineering Task Force (IETF) for ordering the standard positions at the end of 1994) which supported only formatting of the text and embedding idle time schedules.

* In 1995 some offers under expanded standard HTML 3.0 which began to be used as the informal HTML-recommendations embodied in various browsers have been published.

* In May, 1996 the standard of version 3.2 has appeared. For the standard bears the responsibility the organization - a WWW-consortium (W3C - world wide web consortium), she represents association of representatives of the industry and science.

* First release W3C of the specification on HTML 4.0 on December, 18, 1997 has left. The second release (on April, 24, 1998) contained some editorial updatings.

* Standard HTML 4.01 on December, 24, 1999 has left - some mistakes of the previous standard - 4.0 are corrected

* Presence of the standard assumes necessity for the special program (actually VALIDATOR) which checks presence in the HTML-document infringement of specifications according to which the document if these infringements there really are is made.

What is Validator?

Definition:

Validator: a conforming SGML parser that can find and report a reportable markup error if (and only if) one exists.

Validator: the analyzer of conformity and informs standard SGML which finds on a mistake of a marking subject to the report, if (and only if) she exists.

ISO 8896, paragraph 15.4.

Thus the HTML-system is validirujuhhej HTML-system, if

1) She is validirujuhhim the SGML-analyzer agrees ISO 8879, item 15.4;

2) She is capable to process any agreeed with HTML the document;

3) She finds and informs on a mistake in HTML if she exists;

4) She does not inform on a mistake in HTML if she does not exist.

ISO/IEC 15445:2000/DCOR 1:2001 (E), paragraph 2.2.

It is necessary to remember that the html-document - the phenomenon not self-sufficient, and in itself in any way does not look. The site finds the visible form only in a concrete browser. As practice shows - various browsers show concrete page in the different ways (display of pages depends on job of algorithms of the correction which have been built - in a browser, and in different browsers these algorithms are rather various), and, as a rule, all these ways - correct. Actually this one of the important advantages of a network - we shall say, the person with bad sight can increase to itself a font or use reading browser, and for this purpose it is not required to prepare for the separate, special version of a site.

Two most widespread browsers for Windows display pages approximately equally, differing only in such details, as fields and spaces. Browsers for Macintosh or *niksov usually differ from these two more globally. Obvious benefit of presence of the standard what to check one specification it is much easier, than many browsers.

The citation:

«... For people with problems of sight HTML gives promising opportunities to balance them in the rights with usual people at use of base graphic user interface Windows. Tabulared model HTML includes attributes for a mark of each cell to support the high-quality text for the speech interface. The same attributes can be used at support of the automated import and export of the given tables to databases or spreadsheets... »

Many developers (mainly beginning{starting} webs - designers) can not agree with necessity of conformity of a code of the specification: « Validator leaves after itself melancholy sites, kills creativity ». Such opinion arises from simple laziness. The correct HTML-text quite supposes dynamics{changes}, multimedia objects, use of scripts, etc.; simply all these effects can be made competently, and it is possible - illiterately. It is necessary to remember also, that in any creative area it is necessary to study all over again rules, and already then to manage to surpass them. Besides even skilled developers are not insured from mistakes, all of us can suppose typing errors or overlook to close teg. Validator it is capable to trace similar mistakes and in the obvious image to specify a place with incorrect formatting.

Let's result concrete examples of mistakes which are defined{determined} validatorom:

<P> <I> ISO 8896, paragraph 15.4. </P> </I> - it is wrong

(Error: start tag was here).

<P> <I> ISO 8896, paragraph 15.4. </I> </P> - it is correct.

<P> <IMG SRC = "gif gif" alt = "al`"> is inserted the text </P> - incorrectly

(Error: element "P" not allowed here; possible cause is an inline element containing a block-level element)

<IMG SRC = "gif gif" alt = "al`"> <P> is inserted the text </P> - correctly.

If you came to that it is necessary for you to check up your code on conformity of the specification, read some advice: