Where is power steering resevoir on focus 2006 1.6 diesel

There was an issue with the steering in that 04-11 focus... let me see if I can find the problems they've had for you.

Ford Focus fuel pipe leak (2004-2011 cars)
Cars built between July 2004 and February 2005 could have had problems with their fuel return pipes leaking. The pipes were made from material that degraded over time, allowing fuel to seep out.
Ford Focus wiper motor problem (2004-2011 cars)
On early second-generation cars built between April 2003 and March 2005, there were issues reported with the wiper motor. Water could enter the motor through the arm spindle, and if it contained salt, could short-circuit it and cause the motor to overheat. This could lead to trim melting around the motor.

Ford Focus engine failure problem (2004-2011 1.6 TDCi cars)
1.6 TDCi Focus models built between February and June 2004 might have problems with their engines, causing them to cut out. Misaligned oil feeds between the cylinder heads and camshaft bearings reduced oil flow, causing premature wearing of the camshaft bearings and engine seizure.
Ford Focus brake pedal problems (2004-2011 cars)
Cars built between November 2005 and December 2006 could have developed problems with their brake pedals. In particularly cold weather, the pedal could become stiff, as the non-return valve in the pump began to stick.
Ford Focus roll-over protection problems (2004-2011 CC cars)
On some Ford Focus CC models it was found that there were issues with the roll-over protection system. Securing bolts holding the system in place were either loose or not fully tight. Therefore the protection would not be fully effective. Ford should have fixed this for free, so make sure the work has been carried out.
Ford Focus cooling fan problems (2004-2011 1.6 TDCi estate car)
On some Focus 1.6 TDCi estates built between July 2004 and December 2006 there were problems with the cooling fans. Where roads are particularly salty, corrosion could easily occur, reaching as far as the control module. In extreme cases this could cause it to overheat, which could lead to fire.
Ford Focus rear hub bolt problems (2004-2011 cars)
On some Ford Focus models built between February and April 2007 there were problems with the rear hub bolts. They could come loose because they weren't made to the correct design specification.
Ford Focus power steering problems (2004-2011 cars)
Ford Focus models built between April and May 2008 could have had problems with their power steering. Some of the hoses fitted were not to the required specification. The hoses could degrade and allow hydraulic fluid to seep out, which could either cause the power steering to fail or, in more extreme cases, cause fire when the fluid became hot.
Ford Focus risk of fire problem (2004-2011 cars)
Hatchback and estate 1.6 TDCi Ford Focus models, manual and automatic, built between January 2006 and January 2007 may have a risk of fire unless they've had their cooling fans checked. Salty roads could lead to corrosion, overheating and fire if not sorted.
Ford Focus water leaks (2004-2011 cars)
On second-generation cars, some owners have reported water leaking into the cabin. Check any sunroof or window seals before you buy. Also look for damp carpet inside, because it could have become mouldy if left untreated.
Every one of these issues should have been remedied by Ford for free, so make sure the work has been carried out.