You need to define "all funny". Adding a border will increase the width of each item, and may force them to not fit in the rows desired. If you are getting say 3, 1, 3, 1, that is the problem.
Yes, the other classes that cause centering will still be in effect unless you delete them.
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If you specify a border on an element, you will get that border all around it; they don't merge when two are next to each other. You probably want to add something like
border-left-width: 0px;
border-bottom-width: 0px;



