Yeah if u jailbroke it with 4.3.3 and then say... accidently upgraded to 4.3.5 then the SHSH should be saved and thus you can downgrade. Open Cydia and at the top of the Home screen you'll see what SHSH are saved.
TinyUmbrella or iSHSHit will save the SHSH. BTW TinyUmbrella was not able to retrieve all my SHSH but when i used iSHSHit, i could see everything!
Download 4.3.3 firmware onto your computer. Use iTunes and HOLD Option button and click restore in iTunes. Then select the 4.3.3 firmware from your computer and iTunes does the rest!
There are plenty of downgrading YouTube vids so show you step by step!