Hi,

It depends on how do you it to be applied. Do you want all  text areas in your app to have no borders? Or only specific text areas?

If you want all text areas in your app to have no borders, you can modify the custom.css file on your Mendix project. Usually its on YourMendixProjectDirectory\theme\styles\css\custom\custom.css. Then you want to add the following line:

.mx-textarea-input {
    border: none;
}

If you want only specific text areas in your app to have no borders, you can add a class to the property of the text area widget. Right click the widget, tab common, and specify the class.

Then add the following:

.textarea-noborder .mx-textarea-input {
    border: none;
}

This should be the end result:

Hi,

You can use css to do this; style the element with: border: none; 

Best way to do this is to create a specific class for this and add it to the the text area in the modeller.