CSS Import location/define

Hi there,

I have tried to find this on your forum to avoid hassling you but could not locate it.

We have several development and live sites that all have different themes but similar styles. I am trying to import an external CSS file I have on a CDN for multiple small items that will be on several sites. The imported items are nothing major (bits like search button/table styles etc.) but rather than work on wadges of code in each theme I would rather place the code in one area and use the @import code for css - which will also allow me to make global changes.

I have one devsite that shows the change when in the builder but does not when out of it and another site not picking up the changes at all.

What is the best way of using @import for your themes - ie:
@import url("https://mydomain.com/CSS/table_style1.css");