I know I can set "default value" for textbox in D7 webform. Unfortunately, user needs to remove the default value and key in their own information. Actually I want something like placeholder feature. How to do this setting?
You can do this by using Webform Hints module.
This module allows users to enable automatic placeholders to textfields, textareas, select lists, and email fields within a webform created by the Webform module.
That is built in webform 7x-4.7 D7 already (I'm assuming you mean 'textarea' when you say textbox).
- Specific Wedform 'edit'
- Components tab and 'edit' on the particular component
- Scroll down to "Display" header
- After height and width you should have "Placeholder", which is what it says.
Just add you text there. Behaves as placeholder text should.