CSS

background color transparent

div {
	background: transparent
}

background-color: transparent;

 background-color: transparent;
 

css transparent background color

div {
 opacity:25% ; 
}

background color transparent opacity css

/* css semi-transparent background color */
.bg-semi-transparent {
  background-color: #ffffff40!important;
  /* change numbers from 00 to 99 at last of hex code 
  for transpency you want. */
}

css transparent color

#0000000