两个wordpress帖子的特定课程

I have two wordpress posts that I want to give them the same CSS class, in my style sheet I say:

.postid-861 .postid-862 #masthead .site-title a.logo-image img {
display: none;
}

This does not work. Do I miss anything? If I say:

.postid-861 #masthead .site-title a.logo-image img {
    display: none;
    }

It will work for one post only. Please advice

You can give same properties to different classes by using , as below use that code:

.postid-861 #masthead .site-title a.logo-image img , .postid-862 #masthead .site-title a.logo-image img {
   display: none;
}

let's say i have class image and title and i want both to have red background:

.image , .title {
background-color:#a30;
}