Q:

Could it be possible to make css selector affect other elements in the page without javascript? 

For example, I want to make two textboxes have the same style when either is focused:
<div class="divTxt">
    <input type="text" id="a" class="a" />
    <input type="text" id="b" class="b" />
</div>

and the css would be:
.a:focus 
{
    background-color:Blue;
}
.b:focus 
{
    background-color:Yellow;
}

What I need is make a's background-color:Yellow when b is focused and vice versa. 
any possibilities?  Thanks a lot. 

A:

You could try the General Sibling Selector(~) if the input boxes are next to each other. 
Something like:
.a:focus {    background-color:Blue;}
.a:focus~.b {    background-color:Blue;}
.b:focus {    background-color:Yellow;}
.b:focus~.a {    background-color:Yellow;}

Note: Completely untested and a stab in the dark at best!