css

 <style>
input[type=checkbox] {display: none;}
input[type=checkbox] + label:before {
    content: "";
    border: 1px solid #000;
    font-size: 11px;
    line-height: 15px;
    margin: 0 5px 0 0;
    height: 15px;
    width: 15px;
    text-align: center;
    vertical-align: middle;
    display:inline-block;
}
input[type=checkbox]:checked + label:before {
    content: "\2713";
}
</style>

html

<font size="3">
  <input id="check" type="checkbox" name="check">
  <label for="check">Checkbox</label>
</font>