Before you get too excited about the Comodo trust logo and placing it on your site, you may want to read threads about what happens to your store when Comodo's server goes down...
http://forum.x-cart.com/showthread.php?t=47285
--- as to your code -- the first smarty tag should be {literal} ( you have {litera} ) -- typo?
If you search the forum, the solution has been posted -- but there is nothing special about a trust logo -- you just have to put the script into the head in the literal tag -- and place the call to the script where you want it... the "corner of trust" will float -- if you want it to do this.
But in my opinion, you will be better off NOT to do the floating logo -- but that's just my opinion.