title: Why does Enter or Tab key cause a validation on a TextBox?
body: <p>Why does this markup ...</p>
  
  <pre><code>&lt;asp:TextBox ID="TextBox1" runat="server" CausesValidation="False"&gt;&lt;/asp:TextBox&gt;
  &lt;asp:RegularExpressionValidator ID="RegExValidatorTextBox1" runat="server" 
                                  ControlToValidate="TextBox1" 
                                  Text="Invalid date format." 
                                  ValidationExpression="(0[1-9]|[12][0-9]|3[01])[- /.](0[1-9]|1[012])[- /.](19|20)\d\d"&gt;
  &lt;/asp:RegularExpressionValidator&gt;
  </code></pre>
  
  <p>... throw a validation error when I enter some nonsense in the TextBox like "a" and hit only the Enter or Tab key? I' like to have the validation not before I click on a submit button.</p>
  
  <p>(I'm working with VS2008 SP1, .NET 3.5 SP1, if that matters.)</p>