Sunny, it's happened to me before but i don't remember how or why. It's a matter of having hit a button on your keyboard while scrolling usually. Thay's why it only happened on this page likely. i don't remember how it's fixed but that's the likely cause.
They now have zoom controls on touchpads of laptops so you sometimes inadvertently zoom in our out just by accidentally dragging two fingers across your touchpad. Another one of the idiotic marvels of making one operating system for both tablets and pcs.