IR35 is legislation relating to employment status. If your contract does not contain information that clarifies that you are contracting through a limited company, the HMRC could claim that you are actually in effect an employee and this could result in additional tax and NI.
We keep updated on the impact of IR35 cases and are happy to check through your contract for you. However, if you are concerned about your new contract it might be worth you considering having your contract reviewed by the country's leading experts in dealing with IR35 issues, Abbey Tax.
Here is a link to their contract review service: http://www.abbeytax.co.uk/ProductsServices/Contractors/Pages/ContractReviews.aspx