On a search form with only one search term box and one submit button, such as the Quick Search form in the Andornot Starter Kit, the usual user behaviour is to type search terms and press the Enter key. However, there is a longstanding issue with ASP .NET that results in seemingly nothing happening in this case, in some browsers. The form does a weird empty postback because it submits the form, but does not call your ASP.NET submit button's click event: i.e., it does a postback, but does not do anything. The user must instead use the mouse to click the Submit button.
A simple workaround for this is to add a second search box to the form, but make it invisible. For example, add:
<input type="text" style="display:none;" />
Now when the user presses the enter key, the subsequent postback operates as expected (i.e. in the case of the Andornot Starter Kit Quick Search form, it submits the search instead of just doing an "empty" postback that doesn't do anything).