Meta tags, using media query link different CSS files

Use media to query link different CSS files:
<LinkRel= "screen and (min-width:1px) and (max-width:500px)" href="/css/d1.css " /> 
 < link rel=" stylesheet "media=" screen and (min-width:500px) "href="/css/d2.css "/> 
 
      

META Tags:
<Metahttp-equiv="Cache-control"content= " No-cache, No-store, must-revalidate "/> 
 <meta http-equiv=" Pragma "content=" No-cache "/> 
 <meta http-equiv=" Expires "content=" 0 "/>        

Meta is an accessible tag in the head area of the HTML language. 
meta tags for the role of: Search engine Optimization (SEO), define the language of the page, automatically refresh and point to the new page, to achieve the dynamic effect of Web page conversion, control the page buffer, page rating evaluation, control the page Display window and so on. 
 META Tag composition : The META tag has a total of two attributes, each of which is the Http-equiv property and the Name property. 
1. Name Property

A, Keywords (keywords)

Description: Keywords is used to tell search engines what keywords are on your page. 

Example: <metaname= "keywords" content= "information parameters" >

B, description (Website content description)

Description: Description is used to tell search engines the main content of your website. 

Example: <metaname= "description" content= "Information parameters" >

C, Robots (Robot Wizard)

Description: Robots is used to tell the search robot which pages need to be indexed and which pages do not. 

The content parameters are all,none,index,noindex,follow,nofollow. The default is all. 

Example: <metaname= "Robots" content= "None" >

D, author (author)

Description: The author of the callout page

Example: <metaname= "author" content= "Root,[email protected]" >


2. Http-equiv Properties 

when using the <meta> tag with the Http-equiv property, the server adds a name/value pair to the header of the content sent to the browser. 

A, Expires (term)

Description: Can be used to set the expiration time of a Web page. Once the page expires, it must be retransmitted to the server. 

Usage: <metahttp-equiv= "expires" content= "FRI,12JAN200118:18:18GMT" >

Note: The time format of GMT must be used. 

B, Pragma (cache mode)

Description: Prevents the browser from accessing page content from the local computer's cache. 

usage: <metahttp-equiv= "Pragma" content= "No-cache" >

Note: This setting makes it impossible for visitors to browse offline. 

C, Refresh (refreshed)

Description: Automatically refreshes and points to the new page. 

usage: <metahttp-equiv= "Refresh" content= "2; Url=http://www.jb51.net "> (note the following quotes, respectively, before the number of seconds and after the URL)

Note: 2 of these are meant to be automatically refreshed to URL URLs after 2 seconds of stay. 

D, Set-cookie (Cookie setting)

Note: If the page expires, the cookie will be deleted. 

usage: <metahttp-equiv= "Set-cookie" content= "cookievalue=xxx;expires=friday,12-jan-200118:18:18gmt;path=/" >

Note: The time format of GMT must be used. 

E, Window-target (display window settings)

Description: Forces the page to appear on a separate page in the current window. 

usage: <metahttp-equiv= "window-target" content= "_top" >

Note: Used to prevent others from calling their own pages in the frame. 

F, Content-type (setting of the display character set)

Description: Sets the character set used by the page. 

usage: <metahttp-equiv= "content-type" content= "text/html;charset=gb2312" >

G, Content-language (display language Settings)

usage: <metahttp-equiv= "content-language" content= "Information parameters"/>

H, Cache-control Specifies the caching mechanism that requests and responses follow
 
setting Cache-control in a request message or response message does not modify the caching process in another message processing process. 
cache directives on request include No-cache, No-store, Max-age, Max-stale, Min-fresh, only-if-cached,
the directives in the response message include public, private, No-cache, No-store, No-transform, Must-revalidate, Proxy-revalidate, and Max-age. 

Meta tags, using media query link different CSS files