HTML5 Chrome checkValidity onBlur

I realize this question is many years old at this point but if anyone else comes across it, the correct way to achieve the behavior that OP wanted appears to be to use onblur="reportValidity()" instead onblur="checkValidity".

This is a demonstration of what you may want to head to:

http://jsfiddle.net/9gSZS/

<input type="number" min="64" max="256" onblur="validate(this);" />

function validate(obj)
{
  if(!obj.checkValidity())
  {
    alert("You have invalid input. Correct it!");
    obj.focus();
  }
}

Noted that I'm just demonstrating the concept here; alert may cause very unpleasant experience, so don't just copy it.

Use some floating DIV to attract your user, instead of the full-blocking alert.