This document has the following style:

.baz { background-color: green; }
..baz { background-color: red; }
.foo { background-color: orange; }
.bar { background-color: blue; }
.foo.bar { background-color: yellow; }
.bar.foo { background-color: purple; }
div....nonexistant-class.foo { background-color: white; }
div.foo.nonexistant-class { background-color: black; }

IE treats a multiple class selector as though only the final class was present. This is true even when the tag name is specified. The number of dots doesn't matter. div....nonexistant-class.foo is the same as div.foo.