i cant change the online logo

i made a blinkie using blinkies cafe and uploaded it to imgBB and i tried both html full linked and html thumbnail linked. im using the code template thing i found on the website: <style>.online{content: url("url") !important;}</style>

im replacing the url in quotation marks with the image url. can someone help me figure out what im doing wrong? i know basically nothing about html so im probably making a stupid mistake