


Collection of commonly used CSS Hack techniques_html/css_WEB-ITnose
Jun 24, 2016 am 11:56 AM
來源:http://www.ido321.com/938.html
一、什么是CSS Hack?
不同的瀏覽器對CSS的解析結(jié)果是不同的,因此會導(dǎo)致相同的CSS輸出的頁面效果不同,這就需要CSS Hack來解決瀏覽器局部的兼容性問題。而這個(gè)針對不同的瀏覽器寫不同的CSS 代碼的過程,就叫CSS Hack。
CSS Hack常見的有三種形式:CSS屬性Hack、CSS選擇符Hack以及IE條件注釋Hack, Hack主要針對IE瀏覽器。
1、屬性級Hack:比如IE6能識別下劃線”_”和星號” * “,IE7能識別星號” * “,但不能識別下劃線”_”,而firefox兩個(gè)都不能認(rèn)識。
2、選擇符級Hack:比如IE6能識別*html .class{},IE7能識別*+html .class{}或者*:first-child+html .class{}。
3、IE條件注釋Hack:IE條件注釋是微軟從IE5開始就提供的一種非標(biāo)準(zhǔn)邏輯語句。比如針對所有IE:,針對IE6及以下版本:,這類Hack不僅對CSS生效,對寫在判斷語句里面的所有代碼都 會生效。
PS:條件注釋只有在IE瀏覽器下才能執(zhí)行,這個(gè)代碼在非IE瀏覽下被當(dāng)做注釋視而不見??梢酝ㄟ^IE條件注釋載入不同的CSS、JS、HTML和服務(wù)器代碼等。
二、常用的CSS Hack
/* CSS屬性級Hack */color:red; /* 所有瀏覽器可識別*/_color:red; /* 僅IE6 識別 */*color:red; /* IE6、IE7 識別 */+color:red; /* IE6、IE7 識別 */*+color:red; /* IE6、IE7 識別 */[color:red; /* IE6、IE7 識別 */color:red\9; /* IE6、IE7、IE8、IE9 識別 */color:red\0; /* IE8、IE9 識別*/color:red\9\0; /* 僅IE9識別 */color:red \0;??? /* 僅IE9識別 */color:red!important; /* IE6 不識別!important*/
-------------------------------------------------------------/* CSS選擇符級Hack */*html #demo { color:red;} /* 僅IE6 識別 */*+html #demo { color:red;} /* 僅IE7 識別 */body:nth-of-type(1) #demo { color:red;} /* IE9+、FF3.5+、Chrome、Safari、Opera 可以識別 */head:first-child+body #demo { color:red; } /* IE7+、FF、Chrome、Safari、Opera 可以識別 */:root #demo { color:red\9; } : /* 僅IE9識別 */--------------------------------------------------------------/* IE條件注釋Hack */<!--[if IE]>此處內(nèi)容只有IE可見<![endif]--> <!--[if IE 6]>此處內(nèi)容只有IE6.0可見<![endif]--> <!--[if IE 7]>此處內(nèi)容只有IE7.0可見<![endif]--> <!--[if !IE 7]>此處內(nèi)容只有IE7不能識別,其他版本都能識別,當(dāng)然要在IE5以上。<![endif]--><!--[if gt IE 6]> IE6以上版本可識別,IE6無法識別 <![endif]--><!--[if gte IE 7]> IE7以及IE7以上版本可識別 <![endif]--><!--[if lt IE 7]> 低于IE7的版本才能識別,IE7無法識別。 <![endif]--><!--[if lte IE 7]> IE7以及IE7以下版本可識別<![endif]--><!--[if !IE]>此處內(nèi)容只有非IE可見<![endif]-->
三、IE6對!important的支持
!important一般用來做區(qū)分IE6和Firefox等瀏覽器的基本Hack手法。因?yàn)镮E6不支持!important,而Firefox能讀懂!important,其改變了樣式的優(yōu)先級。其實(shí)IE6在某些情況下,也能認(rèn)識!important。
例如:
<style type="text/css">.demo{ color:red !important; color:green;}</style><div class="demo">www.admin10000.com</div>
上面代碼在FF下字體為紅色、IE6下字體為綠色。說明IE6忽視!important的存在。
再來看看:
<style type="text/css"> .demo{ color:red !important; } .demo { color:green; } </style> <div class="demo">www.admin10000.com</div>
如果IE6不認(rèn)!important的話,上面代碼.demo的內(nèi)容應(yīng)該顯示為綠色,可偏偏不是,.demo的內(nèi)容顯示為紅色,說明IE6是認(rèn)得!important的。
兩種情況的區(qū)別就在于:當(dāng)在一個(gè)選擇器中,利用!important改變樣式優(yōu)先級的時(shí)候,IE6下是無效的,后面的樣式覆蓋了前面的,!important被徹底無視了,利用!import
四、IE6下的多選擇符
多類選擇符的寫法。例如:
#my.c1.c2 { color:red;}
.c1.c2 { color:red;}
以上寫法在IE7+/FF/Opera/Safari 等瀏覽器都支持。
但在IE6中,后一個(gè)類名會覆蓋前一個(gè)類名,也就是說,上例被IE6理解為:
#my.c2 { color:red;}
.c2 { color:red;}
同理:
#my.c1.c2.c3 { color:red;}
IE6理解為 #my.c3 {color:red;}
.c1.c2.c3 { color:red;}
IE6理解為 .c3 { color:red; }
所以開發(fā)中用多類來組合實(shí)現(xiàn)css效果的時(shí)候,注意IE6的這個(gè)問題。最好的方法就是,不要用類組合的形式。
?下一篇:IE 8兼容:X-UA-Compatible的解釋

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The key to keep up with HTML standards and best practices is to do it intentionally rather than follow it blindly. First, follow the summary or update logs of official sources such as WHATWG and W3C, understand new tags (such as) and attributes, and use them as references to solve difficult problems; second, subscribe to trusted web development newsletters and blogs, spend 10-15 minutes a week to browse updates, focus on actual use cases rather than just collecting articles; second, use developer tools and linters such as HTMLHint to optimize the code structure through instant feedback; finally, interact with the developer community, share experiences and learn other people's practical skills, so as to continuously improve HTML skills.

The reason for using tags is to improve the semantic structure and accessibility of web pages, make it easier for screen readers and search engines to understand page content, and allow users to quickly jump to core content. Here are the key points: 1. Each page should contain only one element; 2. It should not include content that is repeated across pages (such as sidebars or footers); 3. It can be used in conjunction with ARIA properties to enhance accessibility. Usually located after and before, it is used to wrap unique page content, such as articles, forms or product details, and should be avoided in, or in; to improve accessibility, aria-labeledby or aria-label can be used to clearly identify parts.

To create a basic HTML document, you first need to understand its basic structure and write code in a standard format. 1. Use the declaration document type at the beginning; 2. Use the tag to wrap the entire content; 3. Include and two main parts in it, which are used to store metadata such as titles, style sheet links, etc., and include user-visible content such as titles, paragraphs, pictures and links; 4. Save the file in .html format and open the viewing effect in the browser; 5. Then you can gradually add more elements to enrich the page content. Follow these steps to quickly build a basic web page.

To create an HTML checkbox, use the type attribute to set the element of the checkbox. 1. The basic structure includes id, name and label tags to ensure that clicking text can switch options; 2. Multiple related check boxes should use the same name but different values, and wrap them with fieldset to improve accessibility; 3. Hide native controls when customizing styles and use CSS to design alternative elements while maintaining the complete functions; 4. Ensure availability, pair labels, support keyboard navigation, and avoid relying on only visual prompts. The above steps can help developers correctly implement checkbox components that have both functional and aesthetics.

To reduce the size of HTML files, you need to clean up redundant code, compress content, and optimize structure. 1. Delete unused tags, comments and extra blanks to reduce volume; 2. Move inline CSS and JavaScript to external files and merge multiple scripts or style blocks; 3. Simplify label syntax without affecting parsing, such as omitting optional closed tags or using short attributes; 4. After cleaning, enable server-side compression technologies such as Gzip or Brotli to further reduce the transmission volume. These steps can significantly improve page loading performance without sacrificing functionality.

It is a semantic tag used in HTML5 to define the bottom of the page or content block, usually including copyright information, contact information or navigation links; it can be placed at the bottom of the page or nested in, etc. tags as the end of the block; when using it, you should pay attention to avoid repeated abuse and irrelevant content.

HTMLhasevolvedsignificantlysinceitscreationtomeetthegrowingdemandsofwebdevelopersandusers.Initiallyasimplemarkuplanguageforsharingdocuments,ithasundergonemajorupdates,includingHTML2.0,whichintroducedforms;HTML3.x,whichaddedvisualenhancementsandlayout

ThetabindexattributecontrolshowelementsreceivefocusviatheTabkey,withthreemainvalues:tabindex="0"addsanelementtothenaturaltaborder,tabindex="-1"allowsprogrammaticfocusonly,andtabindex="n"(positivenumber)setsacustomtabbing
