Adjust controls position for all size browsers

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WPF

VS2012

Hi! I want to know how should I fit controls like button, label, datagrid, listbox for all browsers? For example I have got a button there in my WPF web application & I have draged it & placed it there in the center position. If I run my WPF web application it will show my button there in the center position. But when I click on restore down button of my browser to make my browser small then it doesnt show my button there in the center position. It means button doesnt adjust its position by resizing browser`s size. Would you please tell me what should I do & how should I adjust position of my controls with browser`s size?