Image upload not relative

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Hi :) I'm on Win7, Wampserver2.5 and developing my first 5.7.2.1 concrete site - all is well is except for one thing... the image upload isn't relative: If I upload an image and place it inside a block with the image upload dialog it displays fine on localhost, but appears as a '#' on other computers on my LAN.
As a test, I uploaded an image with the dialogue, then took note of it's properties and entered a 'relative' URL in an HTML block eg: '/concrete-folder/application/folder/folder/folder/image-file.jpg' ...this worked fine on the LAN. The same file, when inserted in a content block using the image dialog, fails on attempted LAN viewing - viewing the page source it shows the URL as being eg: 'http://localhost/concrete-folder/application/folder/folder/folder/image-file.jpg' and 'cannot be displayed'...
Where can I set this up in the admin? or a config php file/files if one exists for concrete?
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Edit: scratch that, my laziness at not supplying an alt. tag value for the image (hence the '#' instead of the image over LAN) seems to be the culprit... editing the blocks with images and supplying an alt tag fixed my problems - BAD dog, d0ugal, BAd dog :/
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d0ugal