HTML structure :

<div id="foo1" class="foo" style="background:red">

<div class="bar">

<div class="content"></div>

</div>

</div>

<div id="foo2" class="foo" style="background:blue">

<div class="bar">

<div class="content"></div>

</div>

</div>

Bug of this use :

$( '#foo2' ).children( '.bar .content:first' ).html( 'Some text' );

Writes in the first HTML block.

However this is ok :

$( '#foo2' ).children( '.bar' ).children( '.content:first' ).html( 'Some text' );