Why static method avoided in web application

Question

I learned ( How I don't know) that static method should be avoided in web application.

 

Let suppose a DAL layer is like the code as bellow -

namespace XXX.DAL
{
    public static List<CompanyMaster> GetAllCompanies()
    {
       // code return collection of CompanyMaster
    }
}

so can anyone help me why should I avoid desgin of static here. I search google but do not find anything good stuff around this.