The <p:inputTextarea>
is wider than the <p:panelGrid>
and therefore pushing it far outside the specified width.
You need to set the width on the <p:inputTextarea>
as well.
<p:inputTextarea style="width: 50px;" />
(note: this doesn't take margins into account, so the panel grid is still a bit larger than 50px, but you should now know how to finetune that)
Unrelated to the concrete problem, CSS should go in its own .css
file.