The position of this button is determined by the content - if the text is not sufficient to push the button down to the bottom of the dialog it will not be aligned to the bottom.
If you want to have the buttons positioned on the bottom of the dialog you can add a few simple lines of CSS:
.rwDialogText + div,
.rwDialogText + div + div
You can also make the rules more specific so that they do not affect the RadPrompt directly, as this will position the input at the bottom as well.
The purpose of the KB article is to show how a few lines of CSS can reposition the buttons and the image while keeping the current behavior. You can use it as base and further extend it as you see fit. You can also modify the templates
so that you can work with them more comfortably (e.g. add some classes).
the Telerik team
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