If you set use submit behavior to false, ASP.NET will generate script to handle submit by calling "__doPostBack" method like the following code. The method will add value to event target for telling server which element fire current event.
<script type="text/javascript">
//<![CDATA[
var theForm = document.forms['ctl00'];
if (!theForm) {
theForm = document.ctl00;
}
function __doPostBack(eventTarget, eventArgument) {
if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
theForm.__EVENTTARGET.value = eventTarget;
theForm.__EVENTARGUMENT.value = eventArgument;
theForm.submit();
}
}
//]]>
</script>
<input type="button" name="Button1" value="Submit" onclick="javascript:__doPostBack('Button1','')" id="Button1">
In the other hand, if you set use submit behavior to true, ASP.NET will generate button as input type submit instead of type button. When use click this button, the form will be normally submited.
<input type="submit" name="Button1" value="Submit" id="Button1">
Both ways are not difference at the server-side. But if you set use submit behavior to true, it will generate a bit cleaner XHTML.