Disable/Prevent Copy Paste in a Page with Javascript

< script type = "text/JavaScript" >
//how to prevent cut copy paste
function killCopy(e) {
    return false
}

function reEnable() {
    return true
}
document.onselectstart = new Function("return false")
if (window.sidebar) {
    document.onmousedown = killCopy
    document.onclick = reEnable
} < /script>