Monitor Compatibility W/ PC’s and Mac’s

I am in the process of assisting my wife’s employer with selecting a new PC and doing the data transfer for her outdated Mac. In the interim, to try and save her eyes (She has a 13″ viewable screen), I have recommended that they go ahead and get a 19″ CRT monitor. Are monitors these days compatible with both PC’s and Mac’s. I have read that the newer Macs have an adapter that makes most monitors incompatible with them. Thanks for your time.