In Rails 2.3.5 model I am using
accepts_nested_attributes_for :questions, :reject_if => lambda { |a| a[:content].blank? }
But its rejecting if there is the textbox is not empty.. How can I make it to reject only if there is nothing entered into the textbox ?
Are you confusing reject_if with record validation? The reject_if merely tells the app to ignore that set of nested attributes if a condition is true. In your case, the question's attributes will be ignored if the question's content is blank. If you want to validate or otherwise ensure that the question record(s) have a non blank value for content, you'd put validation in your question model.
You also might consider changing lambda{} to proc{}.