Really. Do you know of any? Could you quote me one or two?
(Just in case someone actually does quote what he thinks is a contradiction, it is up to you to give a competent answer (1 Peter. 3:15). If you can't, don't worry. Simply tell him that you will research it and get back with him and make sure you do).
There are areas of Scripture that are difficult to understand. This does not mean the Bible is untrustworthy. A very good book to have is the Encyclopedia of Bible Difficulties by Gleason Archer, Zondervan Publishing House, (Grand Rapids, Michigan).
Also, CARM has a section on Bible Difficulties