I would like to include line breaks within a Validation Rule Error Message without the use of Visual Force. Is this possible?
If I remember correctly you can embed HTML into error messages that you create from code. I am not sure if the text box for the validation rule will allow you to put HTML into it and that be rendered correctly but I have created custom validation rules by checking a condition and calling the Sobject.addError(errorMessage) onto an object if the condition is met. You can embed HTML into these error message as I have seen it used to link to a visualforce page with a much more thorough description of the error. Creating the error message this way should allow for linebreaks to be embedded since they allow for HTML rendering.