Can't center photos

If your theme has a built-in custom CSS option, use it; otherwise, get a custom CSS plugin and put:

#post img.aligncenter {
display: block;
}

The margin: auto technique won’t work unless you also set display: block.

That worked perfectly! Thanks.

I am very new to wp but just wonder why that would not be an automatic feature?

It is, sort of. WordPress automatically adds the “aligncenter” HTML class to images, but it’s up to theme developers to include the appropriate CSS to actually do the centering. This just looks like an oversight on the theme developer’s part.

If the surrounding paragraph has text-align:center applied (default is left), this should work without any changes to the css file.