Reading AlanBoyd's comment made me think... I use the Firefox browser and if I go to the browser menu I can select the option to zoom in on a web page. If you do this, the percentage of zoom is then shown on the right hand side of the URL in the search bar. You can also use the scroll wheel on a mouse to achieve this, but that probably won't apply if you are on a laptop. The thing is, the browser then saves this setting and every time you return to that particular page it presents it at the same zoom setting as the one previously set. Unless you looked at the search bar you wouldn't necessarily be aware that you weren't seeing 100% of the page. Maybe this feature also appears in other browsers apart from Firefox.
Does any of this chime with your setup?
Just to be clear, I'm not talking about the size of the overall window which is open, as Alan was talking about. The zoom factor applies irrespective of the window size.
