CSS基础

CSS基础

CSS——(cascading style sheets)层叠样式表

      • 用于定义html元素的显示形式(即排版),它有如下优点
        1. 提高页面浏览速度。
        2. 缩短改版时间,降低维护费用。
        3. 更好的控制页面布局。
        4. 实现表现和结构、内容相分离。
        5. 更方便搜索引擎的搜索。
      • 快捷键:ctrl + /  ——是注释和注释取消。

                                              元素 + table —— 标记。

 

 

样式表——可以分为三类:

                   1、嵌入式样式表(先在<head>中定义,再在<body>里调用)其形式如下:

                                             在<head>中定义:<style  type=" text / css">

                                                        /*                              class选择器 (多用这个选择器)                                      */

                                                                                 .Div_name{

                                                                                              color : red ;

                                                                                               background : gray;

                                                                                                    ........

                                                                                                     }

                                                     /*                              id选择器  (尽量少用,以免和后台程序员的id冲突)                                     */

                                                                               #Div_name{

                                                                                               color : red ;

                                                                                               background : gray;

                                                                                                    ........

       

                                                                                                   }

                                                                                      

                                                                                </style>

 

                                             在<body>中调用:< div   class = Div_name >内容< /div >

                                                                              < div   id = Div_name >内容< /div >

 

                                            

                                    2、内联样式表 :在html标记中用一个style属性,如:

                                                                              < div  style = " color : red; background : gray; ">内容</div>                                      

                                     

                                     3、外部样式表:先在<head>中定义,形式为

                                                                              < link  rel = " stylesheet"  type = " text/css"  href = " 外部样式表的url">   

                                                                    然后在连接的这个外部样式表的文件(.css)中写样式定义,如:

                                                                                                         #Div_name{

                                                                                               color : red ;

                                                                                               background : gray;

                                                                                                ......

                                                                                                    }

                                                                    最后在<body>中进行调用

 

选择器——是在<head>中定义,分为如下八种:

                                1、类选择器    class。

                                2、id选择器     id。

                                3、通配符选择器      * 。

                                4、元素选择器

                                5、伪类选择器     有如下几种:

                                                                  a { }

                                                                  a:link{ }            是用在未访问的链接的选择器

                                                                  a:visited{ }      是用在已访问的链接的选择器

                                                                  a:hover{ }        是用在鼠标光标放在其上的链接的选择器(a可以换成其他元素)

                                                                  a:active{ }        是用在获得焦点(如被点击)的链接上的选择器

          •        注意:其上的顺序不能改变   。                                                

                                         6、属性选择器      input  [  type = " text " ]  { }

                               7、包含选择器    用于选择在文档树中一个元素的后代元素,如:若 p元素下有个子元素em,则

                                                                p  em {  }

                               8、伪元素选择器     有如下几种:

                                                                                       元素 :first-line { }    元素内容的第一行

                                                                    元素 :first-letter { }    元素内容的第一个字母

                                                                   元素 :first-child { }    元素的第一个子元素

 

属性单位——分为两种:

                                 1、相对单位:px;em;ex。         (常用)

                                                          1em = 100% = 16px。

                                 2、绝对单位:cm;mm;in;pt;pc(用的比较少,一般打印时用)        

 

 元素内容字体——   

                                      font-family  (字体名称,值可以是中文)   ;

                                      font-style (字体倾斜程度 normal 、italic、oblique)  ; 

                                      font-variant(字体的变体,normal、small-caps 小写变大写) ;   

                                      font-weight(自重,最重的字体为900)    ;

                                      font-size(字体大小)  。          

评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值