Help with css

Hi! 

So i know a little bit of css, however i need help transfering what i know onto here? I already did some basic css but everytime i bring it onto my pack description, all the css work deletes.

Edit: trying dropbox 

Are you uploading your CSS to an external host? Dropbox is an easy/free one if not.

I was, im going to try dropbox right now. I just now realized my mistake. 

If you haven't used dropbox before remember to change the www to dl and remove the dl?=0 at the end of your download link.

Thank you! i have not used dropbox before, so this helps a lot :)