javascript setting the size of a window -

I am trying to set a browser window for a particular size using the code given below Loading the page does not change. I see it through Firefox, but I also saw it through Safari but there is still no change. I am following a number of examples which I found online, and it seems like I am doing what I am doing in the tutorial. What am I doing wrong ????

  & lt ;! DOCTYPE html & gt; & Lt; Html & gt; & Lt; Top & gt; & Lt; Style & gt; Body {background-image: url ('tri_tespic.jpg'); Background repeat: do not repeat; Background attachment: fixed; Background position: center; } & Lt; / Style & gt; & Lt; Script type = "text / javascript" & gt; Function Transitions Screen Sesses (W, H) {window.resizeTo (w, h)} & lt; / Script & gt; & Lt; / Head & gt; & Lt; Body Onload = "Change Screen Size (818,50)" & gt; & Lt; / Body & gt; & Lt; / Html & gt;    
 
 
 This top-level (i.e.) when it is not possible to resize windows popup Is)