Is that a legal and acceptable thing?
thanks in advance

yes its legal

this whole confusinon started beocue teh Aw law says a gun caplable fo acceptin a  magazine  and .....

it may not always be legal.

If you're referring to an AR15 you're fine.  Use anything you like.

However, some rifles require a certian number of US made parts in order to be legal.  If you were to stick a completely foreign made mag into one of these rifles you could upset that parts count and be illegal.  

This is common with some of the postban AK's ar even the G3's... you may need a US made follower, floorplate, mag body etc to remain in a legal configuration.

There are some states where pre-ban high-cap magazines may be illegal, so check your state firearms laws first.
However, in most states it is legal to purchase and use pre-ban magazines in post-ban rifles. These pre-ban magazines being new or used USGI, factory or aftermarket made are legal as long as they were made before the 1994 AW Law.
It is common and probably a smart practice to find pre-ban high-capacity magazines for a good price and purchase as many as you can, as long as it's legal in your state. Even though there are millions of pre-ban mags still available, one day there may be none left and the ones you have are the only high-caps you will ever have and may be worth alot.
Note of advice: If you plan on buying pre-ban mags, stay with USGI or factory made. Thermholds are good too. Cheaper aftermarket brands like USA and TripleK may cause you problems.
Browse around these boards, you'll find more helpful information.

What is the difference between pre and post ban mags?

Nothing physically is different between pre and post ban.post ban are suppose to be marked with the date of manufacture and/or LEO/MILATARY USE ONLY.mmk

Wow, can you imagine the prices for prebans if they had disallowed preban mags in post ban weapons?