element.style {
border: none;
border-top-style: none;
border-right-style: none;
border-bottom-style: none;
border-left-style: none;
border-width: initial;
border-color: initial;
}

element.style {
    border: medium none;
}

element.style {
border: 0;
border-top-width: 0px;
border-right-width: 0px;
border-bottom-width: 0px;
border-left-width: 0px;
border-style: initial;
border-color: initial;
}

element.style {
    border: 0 none;
}

<style>
div {border: 1px solid black; margin: 1em;}
.zerotest div {border: 0;}
.nonetest div {border: none;}
div.setwidth {border-width: 3px;}
div.setstyle {border-style: dashed;}
</style>
<div class="zerotest">
<div class="setwidth">
"Border: 0" and "border-width: 3px"
</div>
<div class="setstyle">
"Border: 0" and "border-style: dashed"
</div>
</div>
<div class="nonetest">
<div class="setwidth">
"Border: none" and "border-width: 3px"
</div>
<div class="setstyle">
"Border: none" and "border-style: dashed"
</div>
</div>