DIV CSS layout, lesson 5, DOCTYPE selection, detailed website production from scratch_html/css_WEB-ITnose

DOCTYPE selection

DOCTYPE selection is also the document type selection, which determines whether the page elements and defined CSS will take effect, because in different DOCTYPEs, the HTML that can be used in the page The elements are different, let’s take a look at them together.

What is DOCTYPE

DOCTYPE is the abbreviation of Document Type (document type). In the page, it is used to specify the version of XHTML (or HTML) used in the page. To make it conform to the standard An indispensable key component of a page is the DOCTYPE statement. Only when the correct DOCTYPE is determined can the logo and CSS in XHTML take effect normally.

What kind of DOCTYPE to choose

In XHTML1.0, there are 3 DTDs (Document Type Definitions) to choose from, namely Transitional, Strict and Framework. (Frameset)

1. Transitional document type

The transitional document type is a DTD with less stringent requirements that allows the use of HTML4.01 logos in the page (the writing method must comply with XHTML grammar standards). The transitional DTD is written as follows:

/p>

"http://www.w3.org /TR/xhtml/DTD/xhtml1-transitional.dtd">

Strict Document Type

A strict document type is a strict DTD that does not allow the use of any presentation layer Identification and attributes, such as , etc., are written as follows:

/p>

"http: //www.w3.org/TR/xhtml/DTD/xhtml1-strict.dtd">

Frame document type

Frame document type is a type used for frame pages DTD. When the page contains frame elements, this DTD must be used. The DTD of the frame is written as follows:

/p>

"http://www.w3.org/TR/xhtml/DTD/xhtml1-frameset.dtd">

Strict DTD is the most ideal document type, but for For web designers who do not know much about WEB standards, it is more suitable to use transitional DTD, because this DTD also allows the use of presentation layer identifiers, elements and attributes and also conforms to the syntax standards of XHTML, which is more suitable for most web page developers.

Benefits of using CSS to control effects

The benefits of using CSS to control performance effects can reduce page code, increase browsing speed, and reduce bandwidth costs. Because the page structure is clear, it can make the web page easier to be viewed. As found by search engines, its best benefits are reflected in the following two aspects:

Benefits for website visitors

1.1 The page code is less, and the file download and display speed is faster quick.

1.2 The semantic structure is clear and convenient for more users to access.

1.3 Structure and presentation are separated and can be accessed by more devices.

1.4 The performance effect is independent, users can choose their favorite style.

Benefits for website owners

2.1 Simple code and fewer components for easy maintenance.

2.2 has low bandwidth requirements and can save costs.

2.3 The page structure has clear semantics and is easy to search by search engines.

2.4 The separation of structure and presentation makes it easier to modify the appearance of the page without changing the content of the page.

2.5 can conveniently provide a printed version by calling different style files.

2.6 The page structure is clear and the website becomes easier to use.

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