User Portlet User Portlet

Discussions
When I evaluate the whole notebook by Evaluation -> Evaluate Notebook, some of the output cells go gray (tables). This does not happen if I go cell by cell and hit enter on numeric keyboard. What is the problem? Does Evaluate Notebook even evaluate...
As I have mentioned at the end of the post, *"NumericQ is not always the good solution. What if I want to pass infinity which does not evaluate true as NumericQ or if I am using units!"*
I have: LogLinearPlot[ f1[bg] - f2[bg], {bg, 100, 10000000}] and I get: Power::infy: Infinite expression 1/0. encountered. >> Power::infy: Infinite expression 1/Sqrt[0.] encountered. >> Infinity::indet:...