I have created some rukles for a div but let´s make it short.

if I have

Code CSS:
div {
background-color:red;
}
.somestyle {
background-color:blue;
}

Then I have this

Code HTML4Strict:
<div>some content x</div>
<div>some content y</div>
<div>some content z</div>
<div>some content a</div>
<div>some content b</div>

That would create 5 divs with each having a red background right?

now on windows load one of those divs is added the class name somestyle but the background color is not changing to blue it stays red.

how can I force it to use the background color in that css rule?

after javascript is executed

Code HTML4Strict:
<div class="somestyle" >some content x</div>
<div>some content y</div>
<div>some content z</div>
<div>some content a</div>
<div>some content b</div>