Just turn the warnings off in the Preferences | Warnings.
However, I would caution against changing the defaults. Most new user errors are due redefining built-in and othe variables and functions.
Redefinitions also run the risk of confusing future users, including yourself, into thinking that a particular variable or function is something different from the redefinition, because they missed the actual redefinition. It's a bad slippery slope.
"New Users" hell, I've been using MathCAD for over 10 years and I still try to use "A" for area and "m" for mass. Without the squiggly line I would be in trouble most of the time. In the last year I've started trying to always subscript every variable (with the ".") and have found that I have many fewer outrageous results.
