I am having trouble centering objects. I note there is no command as such, but that two guides can be used. When I do this, everything looks fine in VSD; however, when I preview the site, one or more of the objects will not be centered. I am designing the site in a lower resolution than my monitor, but I would not think that should affect centering. If that is perhaps the issue, how does one make a design that will show the same alignments at various resolutions? Anyway, I would appreciate anyones advice. I am new to VSD and know NOTHING about html.

Gary, sometimes the margins and padding around objects can cause display differences in various browsers. You won't see this within VSD, since it's a WYSIWYG and inserts the code for you.
But, just in case some items are overlapping and getting shifted, you could group them together. Get them lined up how you want then shift-click to select them all then click Object (top menu) > Group.

Just to be sure everything works well, I'd keep everything the same resolution so no surprises there.