Compare this HTML document with its XHTML counterpart
HTML does not allow the 'object' tag to be closed using the XML empty-element tag syntax <object ... />. It must be closed with a separate closing </object> tag. If it isn't, some user-agents will treat the 'object' element as if it hasn't been closed. As a result the rest of the document will not be shown (assuming the content embedded by the <object> tag is supported by the user-agent). This is because the rest of the document is treated as alternative content, only to be shown if the embedded content isn't recognised. This HTML document contains an <object/> tag closed using the XML empty-element tag directly after this paragraph, so if your user-agent works this way this is the last text you'll see (view the source to see the paragraph that follows).
You can see this? In that case your user-agent allows the XML empty-element tag syntax in HTML. Be aware that some don't though. Notably Mozilla.