Hi,
You can use a function in your aspx.cs file which will store the tool tip strings . As suggested above you can save this in Database / Cookie and session.
When ever any users logs in you can fetch this flag (show / no show) to call this function which sets tooltip property of all controls.
if(ShowFlag)
{
SetTootips();
}
Your SetTooltips should be like this
private void SetTootips()
{
TextBox1.ToolTip = "Blablabla";
TextBox2.ToolTip = "Blablabla";
TextBox3.ToolTip = "Blablabla";
Button1.ToolTip = "Blablabla";
Button2.ToolTip = "Blablabla";
Image1.ToolTip = "Blablabla";
}
As an UI suggestion, you can use a link button on your master page, so that user can set this option on and off at any time.