Is background-color:none valid CSS?

You probably want transparent as none is not a valid background-color value.

The CSS 2.1 spec states the following for the background-color property:

Value: <color> | transparent | inherit

<color> can be either a keyword or a numerical representation of a colour. Valid color keywords are:

aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, orange, purple, red, silver, teal, white, and yellow

transparent and inherit are valid keywords in their own right, but none is not.

No, use transparent instead none . See working example here in this example if you will change transparent to none it will not work

use like .class { background-color:transparent; }

Where .class is what you will name your transparent class.

The answer is no.

Incorrect

.class {
    background-color: none; /* do not do this */
}

.class {
    background-color: transparent;
}

background-color: transparent accomplishes the same thing what you wanted to do with background-color: none.