This topic isn't strictly about sitepatching but will change site compatibility. Mostly for the better but there could be unexpected side effects on sites that expect certain behavior - thus becoming targets for site patching. More on that later.
Let's take the last first, object parsing. Assume the following quite typical markup (simplified):
<object classid="clsid:CAFEEFAC-0016-0000-FFFF-ABCDEFFEDCBA"> <param name="code" value="foo.class"> <embed type="application/x-java-applet" code="foo.class"> </object>
The object is here meant for IE. IE recognizes the classid and invokes the Java ActiveX control based on it. Other browsers don't understand the object and fall back to using the embed where there is a type attribute they can understand.