Develop web site for iphone/ipad screen

Hello i need to add new additions to one of my client's web site that will fit to iphone and ipad and most of mobile devices. this new part should fit to the screen size of browsing mobile device. part of this will be added paypal payment gateway too. back end will connect to mysql database . (more info will be in private) previous samples related to that area (mobile web app development) will get high priority when the provider consider. i do not think this is complicated project. so dont bid too big amounts