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+=========================================
+Refactoring the CSSs with UI properties
+=========================================
+
+Overview
+=========
+
+Managing styles progressively became difficult in CubicWeb. The
+introduction of uiprops is an attempt to fix this problem.
+
+The goal is to make it possible to use variables in our CSSs.
+
+These variables are defined or computed in the uiprops.py python file
+and inserted in the CSS using the Python string interpolation syntax.
+
+A quick example, put in ``uiprops.py``::
+
+  defaultBgColor = '#eee'
+
+and in your css::
+
+  body { background-color: %(defaultBgColor)s; }
+
+
+The good practices are:
+
+- define a variable in uiprops to avoid repetitions in the CSS
+  (colors, borders, fonts, etc.)
+
+- define a variable in uiprops when you need to compute values
+  (compute a color palette, etc.)
+
+The algorithm implemented in CubicWeb is the following:
+
+- read uiprops file while walk up the chain of cube dependencies: if
+  cube myblog depends on cube comment, the variables defined in myblog
+  will have precedence over the ones in comment
+
+- replace the %(varname)s in all the CSSs of all the cubes
+
+Keep in mind that the browser will then interpret the CSSs and apply
+the standard cascading mechanism.