Hi,
You mean a javascript alert? If so no, this is determined by the browser.
Alternatives might be to design a layer that looks the way you want and then
use the Show/Hide Layer behaviour to display it.
I think you can do vbscript alerts and have the different sorts of error boxes
like "information" (blue circle/with letter 'i') or the "alert" (yellow
triangle/exclaimation) or "critical" (red circle/letter "X")....I know these can
be done in Visual Basic itself and vbscript is not quite VB, but do those alert
box attributes follow through in vbscript?