Use firebug to identify the right css class and apply this style in your custom theming. I think this class is using position:absolute with the top and left attributes. Modify these attributes in your custom theme.
Edit:
Add this to your custom theme:
.mendixToaster {
top:100px !important; (adjust these to specify the position of the element)
right:50px !important; (adjust these to specify the position of the element)
}