Why am I in a sort of XRay mode?

[Joe Wood]

I have See Hidden Geometry turned off, it's obviously in Shaded With Textures view, but all of a sudden I can sort of see thru faces (stucco wall, roof plane) to lines behind,I didn't touch anything, was just exporting images, so what happened?

win 7, SUp 2015 nvidia card

[Charlie__V]

You have enabled back edges.....

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[Joe Wood]

ay yi Yiii, that was an easy one thanks!

[cotty]

It has assigned the shortcut 'k'...