May not be a permanent fix, however, for chrome you can edit HTML on the fly and it would render just like that, think you access it by pressing F12, is there no way you can change the HTML coding and change the size variable within the code. I don't use mydlink as my cameras are running on LAN connection only.
However, could you not do this instead - http://forums.dlink.com/index.php?topic=50319.msg185900#msg185900 - and save it as a HTML page on the client PC? So all you'd have to do is open up the HTML file?