Problem: My viewport is stationary. and I can't zoom in anymore. I'm not rotating around my mesh, but around the view, so to speak. What can I do to remedy? Much thanks!
If you are "lost in space" you can press the Home button to view all objects in your scene, or select an object in the outliner and press Numpad "." to view active object. Also check the clip values in the "N" properties panel: in my example all objects closer than 1 cm or far more than 1 km will be greyed out, and you can change thoose values.