Hide/unhide DIV tag

How to hide / unhide the div tag in aspx page.

jscript

function Show(divId)
{
document.getElementById(divId).style.visible ='visible';
}

function Hide(divId)
{
document.getElementById(divId).style.visible ='hidden';
}

HTML
<input type=button onclick="Hide('someDivId');" />
<input type=button onclick="Show('someDivId');" />