html - I need to apply the css for a specific class and id -

i need apply css specific class and id of element this.

<div class="contents" id="contents">

i tried

#contents .contents { ... }

but doesn't seem work.

how apply css specific class , id ?

added

with

#contents.contents {...}

it works ok.

#contents.contents { ... }

… should work fine. problem somewhere in code haven't shared us.

#contents .contents { ... }

… means "an element member of class contents descendent of element id contents"