When navigating from a page that fits your browser to one that overflows you can see page shifting. Here's a tip from Lee White to make the vertical scroll bar always visible to prevent the shifting.
Using Windows Explorer go into the \chrome folder using
Select the oddly named AAAAAAAA.Default folder. Now select the Chrome folder. If you don't have a userContent.css file you should have userContent-example.css so make a copy of it and rename it to userContent.css.
Open it with an ASCII editor and add the two lines below...