maximize the window size,the page size not following the window size

when I adjust the size of window,and input the URL to load page,the page loaded.and then I maximize the window,but the page size keep the same like just now.
all I want to do is when maximize the window,the size of page could following the window to maximize,but now,it’s no use.how could I do?somebody help me?

yeah,I’v got the solution,setWidth(“-1px”);the problem solved