I am building a template for my institution and have done this using css within the html. I have so many pages that use this code that it is becoming impossible to maintain. I would like to use a style sheet instead but keep on reading that this could cause conflict.

The additions I am making concern quite simple code i.e colours, border-radius, grid-row etc. There is no javascript necessary and so far I have used the canvas whitelist tagsonly. What would be the objections to doing this? And if one were to upload a css stylesheet using only whitelist tags, would this be a safe option and less susceptible to change? Also, do the warnings for using your own stylesheet only concern using javascript? 

Any information on this would be appreciated.

Tamar