If there is a page with pictures which don't fit into your browser window size then you can paste small javascript into address bar and execute it.
For example, this code will resize all pictures wider than 800px to 800px:
javascript:var%20i,L=document.images.length;for(i=0;i<L;++i){document.images[i].style.maxWidth='800px'};false();
You can save this code into your browser bookmarks for convenience.