Css + javascript stuff

so I have this in css on a div:

display: none;

and the problem is that in javascript “style.display” isn’t the same as the “display” in css
If I do

alert(somediv.style.display);

then it’s blank

I need to somehow have the default of “style.display” to be “none” or something. Can’t I somehow do it with css?

I could always use a for loop to change the “style.display” of all my divs to “none” but is there a more decent way out of this?