How to style an element in a global region without affecting the same elements on other pages/posts?

Dear WPMU Team

How can I style an element which is placed in a globale element and which also exists on other pages with the same ID but without affecting the same elements on other pages/posts?
Below the code I first implemented in the global CSS area which then affected also the same elements on other pages. I then tried to put the code as it is directly in the element, unfortunately it did not work.
@media screen and (min-width:1025px) {
.upfront #page #upfront-region-container-main .upfront-output-uwidget {
margin-top: 50px;
width: 225px;
position: fixed!important;
z-index: 9999!important;
}
}

Do you have any idea how I can solve this issue?

Many thanks.

Kind regards,
Markus