CSS customization applies only to main page but not to "tag" pages

Hi! I am new to writefreely. I added a custom CSS, which shows a preview of the posts in my main page:

body#collection #wrapper article {
max-height: 450px;
overflow: hidden;
position: relative;
body#collection #wrapper article:before{
content: ‘’;
pointer-events: none;
width: 100%;
height: 70%;
bottom: 0;
position: absolute;
background: linear-gradient(transparent 100px, #FFFFFF);

/* Blog description (underneath title) on index page */
header p.description {
font-style: italic;

But that applies only to the main page. When I go into some “tag”, like for example


Then it shows the entire text of the posts, and not a preview.
How do I make that my CSS customization to apply not only to the main page, but also to the “tag” pages?

Thank you very much and I apologize if I made some mistake by my posting here. I am new here.

Thanks for sharing this idea, I had almost similar issue in my blog.
How to find Z score in Statistics using its formula

And how did you solve it? I still have not found a solution.