"certified" copies for I-130 Filing

Does anyone know if copies of supporting document for I-130 need to be "certified" copies (still unsure what that means) or can they just be copies made?  Copies of passports, my US birth certificate, marriage certificates and the ex's divorce decrees I'm speaking of mainly.

Thanks - I've read conflicting things online and just getting UK Yankee take on what to do. 

Any advice or redirecting me to another thread greatly appreciated.

Normal photocopies are fine. The US Embassy site on how to do the I-130 is pretty clear on that you do not send original documents (ie certified copies). You just have to bring the originals to the visa interview.

Thanks - that is how I was hoping it worked.