Custom Chekbox

HTML

<form action="" method="GET">
    <input class="" type="checkbox" id="chk" name="chk" value="1" /><label for="chk">Tick me</label>
    <input type="submit" value="Submit" />
</form>

CSS

.styled-checkbox {
    opacity: 0;
    filter: alpha(opacity=0);
}
.styled-checkbox + label {
    position: relative;
}
.styled-checkbox + label:before,
.lt-ie8 .checkbox-replacement {
    content: '';
    display: inline-block;
    visibility: visible;
    left: 0;
    width: 1em;
    height: 1em;
    margin: 0 0.3em 0 -1em;
    line-height: 0.6;
    text-align: center;
    /* Put checkbox styles here: */
    border: 1px solid red;
    border-radius: 50%;
    
}
.styled-checkbox:checked + label:before,
.lt-ie9 .styled-checkbox.checked + label:before {
    content: '✔';
}
#chk
{
  border: 1px solid red;
  border-radius: 50%;
  
}