Using both sprites and custom images..

[Mostafa.Shiraali]

if you do not know what are you doing , So it's better not to change anything and give it to someone who knows what they're doing. 
if I want give you a example :
if you have a element like this

<span class="myclass">button</span>

and style is like

.myclass {
...
background: url('images/buttons/closed.png') no-repeat;
...
}

you have two way =>
first add a unique classname to that element like

<span class="myclass newclass">button</span>

then overwrite background atrributes like this :

.newclass{
...
background: unset !important;
...
}

or replace current class with new classname like

<span class="newclass">button</span>

then in new class name add all css atrributes except background

.newclass{
...
...
}

and if you not know do this and you want only disable background attribute for this element you can add as inline code too like this

<span class="myclass" style="background: unset !important;">button</span>