I need to change the style of the \"OK\" Button in an alert box.
The alert box is a system object, and not subject to CSS. To do this style of thing you would need to create an HTML element and mimic the alert()
functionality. The jQuery UI Dialogue does a lot of the work for you, working basically as I have described: Link.
jQuery UI Dialog - Default functionality
This is the default dialog which is useful for displaying information. The dialog window can be moved, resized and closed with the 'x' icon.