jQuery plugin positioning

With the development of one project, the diva positioning in the middle of the page arose regardless of the width of the diva and whether there is a scroll on the page.
If the page fits on the screen - you can do it through sss (position: absolute; left i top), but here you must take into account the width of the diva in each version.
If scrolling appears on the page - then there are some problems.
Since the last time (and in that project too) I use javascript framework jQuery - I decided to make it into a plugin.
This is how the positioning plugin appeared.

The plugin has 2 methods:
positioning (leftOffset, topOffset, scroll) - position the element on the page

leftOffset - horizontal shift
topOffset - vertical shift
scroll is a parameter that specifies the positioning relative to the “absolute” upper left point of the browser, or positioning relative to the upper left point of the already scrolled page.
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The call centering () - positions the element exactly in the center of the page.

Plugin tested in FF 3.0, IE6.0 +, Safari 3.1, Opera 9.6
An example can be found here.
yablog.org.ua/jquery/index.html
At the bottom of the page there are 3 buttons - clicking on them you can see the plugin in action