If you have element with multiple classes (regarding comments at question), like
<div class="ui-btn ui-input-btn ui-corner-all ui-shadow">
and you need to set styles, you have two options:
First is to set background to one of these classes, eg.
.ui-corner-all {background: yellow;}
The second one, if you want to target just element with all classes, the correct selector is
.ui-btn.ui-input-btn.ui-corner-all.ui-shadow {background: yellow}
Your attempt .ui-block-b .ui-btn .ui-input-btn .ui-corner-all .ui-shadow
tried to find .ui-shadow
in .ui-corner-all
in .ui-input-btn
in .ui-btn
in .ui-block-b
like:
<div class="ui-block-b">
<div class="ui-btn">
<div class="ui-input-btn">
<div class="ui-corner-all">
<button class="ui-shadow">
</div>
</div>
</div>
</div>
This HTML markup doesn't exist.