Changing Post Order

I've been messing with the the code and it's getting closer to what I want.
Yet the problem I reported last still I remains. I can't select only the post excerpts displayed on the home page (index).

The below is the code I've inserted into the site.

@media screen and (max-width: 400px) {
body.home {float: none; width: 100%;}
}
@media screen and (min-width: 600px) {
body.home {
float: left ;
width: 50%;
padding: 0 15px;}

I've set the grid to 12 to make room for the 2 columns. The problem: the post no longer float and the homepage is no longer centered.

I've been messing with it for some time, can't really figure it out.

Any help would be appreciated.
Thanks,