> is there any way to know a page's size before 
> downloading any file? 

Yes, but *only* if the server gives this information 
in the headers (Content-Length field). This 
information is being used by the engine to limit the 
file sizes, and shutdown the connection if necessary. 
But sometimes, the engine will not have any size 
information and therefore will have to download some 
data to find that the file was too big (yes, this is a 
pitty)