What makes jQuery easy to use is that you don't have to apply attributes to each element. The jQuery object contains an array of elements, and the methods of the jQuery object applies the same attributes to all the elements in the array.
There is also a shorter form for $(document).ready(function(){...}) in $(function(){...}).
So, this is all you need:
$(function(){
$('div.easy_editor').css('border','9px solid red');
});
If you want the code to work for any element with that class, you can just specify the class in the selector without the tag name:
$(function(){
$('.easy_editor').css('border','9px solid red');
});