This phase I trial is studying the side effects and best dose of gefitinib and capecitabine in treating patients with advanced solid tumors. Biological therapies such as gefitinib may interfere with the growth of tumor cells and slow the growth of solid tumors. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining gefitinib and capecitabine may kill more tumor cells