From Xojo Documentation

Property (As Integer )
aWebControl.HorizontalCenter = newIntegerValue
IntegerValue = aWebControl.HorizontalCenter

New in 2010r5

Supported for all project types and targets.

Specifies the horizontal center of a control on a web page, which can be used to easily center a control on the page.


For example, to center a control horizontally:

Button1.HorizontalCenter = Self.Width / 2

(Self being a WebPage in this case).