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HomeWeb Front-endHTML TutorialCSS text-indent: -9999px;_html/css_WEB-ITnose

   建站过过程中朋友喜欢把网站名称用H1表示,但从美观考虑,要用logo图片来代替h1,这时需要隐藏h1内的这段文字,但又不能对搜索引擎不友好,否则就失去了定义h1标签的意义。

   在CSS中如何以图代字,找了一下CSS隐藏文字的方法,有以下几条:

   1、display:none;

   这个大家普遍说法是,搜索引擎可能认为被隐藏的文字属于垃圾信息而被忽略,不为隐藏的对象保留物理占位空间。GG也搜CSS文件?不过如果用这个方法,

如何设计,也是难题。

   2、visibility:hidden;

   和display:none;相对应,为隐藏的对象保留物理占位空间。  

   3、overflow:hidden;

   这是网上用的最多的方法,但是我认为对于隐藏h1标签的“站点名称”文字,不太合适,原因我在最后说。

.texthidden{  display:block;  overflow:hidden;  width:0;  height:0;}

  4、positon:absolute;

  用绝对定位将其推出可视区,不过虽然可视性不存在,但仍占据物理空间,与隐藏文字的宗旨相背,另外我个人不喜欢用绝对坐标定位magin这个属性,margin在不同浏览器中总是带来不可预料的Bug。

.texthidden{  positon:absolute;  margin-top:-9999px;  margin-left:-9999px;}

  5、text-indent:-9999px;

  把h1作为一个块来显示(display:block;),指定长宽(和图片一样大小),然后指定h1的背景图片,也就是将我们需要的图片作为h1这个标签的背景。而h1标签中插入的,仍然是作为字符形式出现的博客标题,然后用text-indent:-9999px;将文字甩到屏幕看不到的地方,9999px应该是足够了,谁的屏幕也没那么大吧。

h1 a{  height:30px;  width:165px;  float:left;  text-indent:-9999px;  background-image:url(images/logo.gif);  background-repeat:no-repeat;  display:block;  position:relative;}

  

  js助手

  

  在h1使用上语义明确,符合语义化定义。text-indent就是首行缩进,大家都在中文段落,首行空两格用过它。这里通过负值缩进,使文字超出可视区,而这时h1下的背景就显示出来了,h1中包含的标签又不影响使用,对于隐藏文字“站点名称”应该是最佳方案了。但对于多段文字的隐藏这个方法就不适合了。

  这里还有个问题,就是点击

链接时,会产生一个虚线框,对于IE还好,没什么问题,虚线框只是在背影图片大小。但是Firefox就有些麻烦,它把缩进的文字范围也包含进来了,这样不是很美观。

  于是需要屏掉点击时产生的虚线框,IE和FF屏虚线框方法不一样。IE采用的遍历方法(HTC,css表达式)有些耗系统资源,正好我们只需要隐藏FF下的虚线框就行了,IE就不管了,说一下Firefox如何去掉链接的虚线框的方法。

a{  outline:none;/*去掉Firefox点击时产生的虚线框*/}

PS:全文都只是作者的观点,至于使用text-indent:-9999px;来解决问题是否可行,有人赞同有人反对。所以还是有待进一步讨论。

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