I created this HTML button, and after styling it with CSS, every time it's clicked a blue selection border appears around it. Is there any way to fix this? I know that the default unchanged element does not do this when i create it, so I'm thinking it must have something to do with the CSS I added.
HTML:
<button type="button" class="drop-button" >-</button>
CSS:
.drop-button {
    background-color: #343436;
    color: #FFFFFF;
    border: none;
    border-radius: 5px;
    margin-right: 8px;
    margin-left: 4px;
    height: 20px;
    width: 25px;
    font-size: 20px;
    vertical-align: middle;
    line-height: 0px;
}
 
     
     
    