The best way is to use two really handy plone views that are only for this purpose. The interface that defines them is at https://svn.plone.org/svn/plone/plone.app.layout/trunk/plone/app/layout/globals/interfaces.py if you want to check it out.
<tal:block
tal:define="our_url context/@@plone_context_state/canonical_object_url;
home_url context/@@plone_portal_state/portal_url;"
tal:condition="python:our_url == home_url">
HERE GOES YOUR STUFF
</tal:block>
@@plone_context_state @@plone_portal_state , . context/@@plone_context_state/canonical_object_url , URL- , : -)