Is there such a thing?
Like
.el{
background-image: don_change;
}
I have to define the property, but I don’t want it to change in certain conditions (the element has a default value for that property in another .css file, which should be used).
If the value is a valid property like url(image.jpg), then it should be applied
I think it should work using the !important rule: http://www.w3.org/TR/CSS2/cascade.html#important-rules