I have the following line of css code that works in Chrome but not Mozilla.
mask-image: radial-gradient(ellipse 20px 20px at 50% 50%, black 40%, transparent 50%);
Thank you in advance! 
I have the following line of css code that works in Chrome but not Mozilla.
mask-image: radial-gradient(ellipse 20px 20px at 50% 50%, black 40%, transparent 50%);
Thank you in advance!
In the documentation of this statement it is explained that firefox does not handle support for this instruction. -webkit-mask-image-
You have to put the prefixes for each browser I hope this is what you are looking for
#grad {
background: -webkit-radial-gradient(red, green, blue); /* Safari 5.1- 6.0 */
background: -o-radial-gradient(red, green, blue); /* Opera 11.6-12.0 */
background: -moz-radial-gradient(red, green, blue); /* Firefox 3.6-15 */
background: radial-gradient(red, green, blue); /* Standard syntax */
}
In case you want it to work in Firefox :
mask-image: -moz-radial-gradient(ellipse 20px 20px at 50% 50%, black 40%,
transparent 50%);
I found this page that may be able to serve you. link