How to add Rounded corners for all TextBoxes in Website?

Question

Hi to all.In my website i need to make all the TextBoxes  rounded corner in the entire website.I know how to do it in a single page by adding a css class property of TextBox to a class name that was added in a CSS file by adding reference to that css file in source view of the page.but i've nearly 32 pages in my project.How to do all TextBoxes rounded corner in single shot.Please help me in this scenario.

                                                                   Thanks in Advance.