parts of my style.css are preferentially ignored?

I uploaded a very simple style.css file, clicked "go to my page," and it displays everything except my <cop> tag (for 5px text size). The same style.css file works fine when I open the html file in a browser offline. When I look at the "preview" of my uploaded style.css file, I am surprised to find that my <cop> tag is not there! Then, when I go to edit the style.css file using the alterVista editing interface, I am even more surprised to discover that the <cop> tag is there!

What is going on here?

Ok, today everything suddenly works fine. I guess the server takes a long time to publish changes to the webpage? Or maybe something glitched out temporarily? Strange.

Probably a cache problem of your browser. You have to type CTRL+F5 to clean the cache and update a page.