Using CSS selector specifity over selector ID's? -


in class teached avoid creating id's in html can use them identify element in css file. instead must use selector specifity as possible.

take example simple html:

<body>   <div>      <div>        <div>           div want style.        </div>      </div>   </div> </body>

is better use this:

body > div > div > div{      color: blue; }

or give element id (let's take 'middle') , use this:

#middle{      color: blue; }

what differences (if @ all) performance , usability wise?

the difference in speed between ids , classes in modern browsers negligible in real world situations not issue. therefore current main-line thinking use classes clarity , specifity needed. way avoid specifity wars , balances maintainability code purity.

<body>   <div>      <div class="more-specific-if-needed">        <div class="middle">           div want style.        </div>      </div>   </div> </body>  .make-more-specific-if-needed .middle {     /* cool styles */ }

or use chained selectors gain specifity. split styles in separate structure based build styles , appearance based theme styles. 

<body>   <div>      <div>        <div class="semantic-role theme">           div want style.        </div>      </div>   </div> </body>  .semantic-role.theme {     /* cool styles */ }

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