css - Unwanted border in :before/:after pseudo-elements -

the code below works fine on desktop browsers. when applied in android webview, there seems border. ideas on how should deal this?

.container{           width: 100px;           height: 50px;           background-color: #fff;           color: #000;           padding: 5px;           position: relative;        } .container:before{           content: "";           border-left: 20px solid transparent;           border-bottom: 50px solid #fff;           position: absolute;           left: -20px;           top: 0;        } 

try adding right:100% instead of left: -20px or give 1 less actual left: -19px;