Hi all i am atempting to model a tyre from a tutorial by Andrew Price everything is going well but i’m having a problem with my viewports my orthogrpahic views are not displaying correctly what i mean by this is that the top front and side views are not lining up properly ie dead on, when i first open blender the views display correctly only when i am working on the model this happens how can i reset my views thanks in advance 
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Straight from Wiki:
You can select the viewing direction for a 3D Viewport with the View Menu entries (A 3D Viewport’s view menu.) or by pressing the hotkeys NumPad 3 for “side”, NumPad 1 for “front”, NumPad 7 for “top”. You can select the opposite directions if you hold Ctrl while using the same numpad shortcuts. Finally NumPad 0 gives access to the “Camera” viewpoint.
This is with your cursor in that viewport window at the time you press the number.
There is a menu under 3D view port for Background Image. In that dialog box the image can be translated and scaled. That’s one way to deal with background image.
Other issue that happened to me is that if all that images were setup using 3 different 3D view ports, the view port can’t be swapped about after background images get placed. Background images get all mixed up if you do that.