Inline block confirm messages I have a contact (web)form in my sidebar on my site and I would like to display a custom confirm message when a users submits the form. However, this message should replace the contact form.

I've tried with Inline Messages or with the form-settings (no-redirect), but every solutions just redirects the entire website to the node and displays the message inline. So, that not what I want, obviously...

So, is there a solution where the content of the page remains unchanged, but when submitting the form in the sidebar, only the sidebar refreshes and shows the confirmation message?
The Webform Ajax module will give you the functionality you describe. Here is a quote about it (from the module's project page):

... adds AJAX support to Webform (3.0 and above).
As a first step it focusses to simply add form AJAX paging and submit. Form submissions get ajaxified including prev/next pages. Especially for multipage forms, this leads to faster loading (less data transfer), better usability and finally smaller server load.