How to solve problem: Visual Studio cannot recognize name space even already added related project as reference?

Check two projects’ target framework are same.
My case: one target framework is .Net 4.0, another is .Net 4.5

CSS box model and element vertical align issue

http://krugerdavid.com/journal/understanding-blueprintcss/
Many vertical align issues are related to margine and padding value, so understand css box model will be helpful.