A nice DOM property I bet most of you have missed ...

Have you ever heard about the defaultValue and the defaultChecked properties?
They seems to be a standard DOM properties so the major browsers seem to support them.
What they do?
The defaultValue property is about textboxes (input type="text") and it will contain the value which the textbox has at the time it was rendered on the page.
The defaultChecked property is almost the same, it is about a checkbox and it tells you whether the checkbox was rendered checked or not.

So doing something like:

function hasTextBoxChanged(textBox) {
return textBox.defaultValue == textBox.value;
}

would tell you whether the textbox passed as an argument has changed its value since it was rendered on the page.

Same function for checkbox would be something like:

function hasCheckBoxChanged(checkbox) {
return checkbox.defaultChecked == checkbox.checked;
}

I find those properties very helpful. If you play a bit with jQuery you can find a real life application of them.
I am however wondering if there are such properties for dropdowns and some other controls.
If I find - I'll definatelly post again.

Hope it helps someone outthere ...

P.S. if the control is a part of update panel and it was udpated in the code behind it will not be counted as a change as the defaultValue / defaultChecked properties will be set again (those properties are taken to be the value of the control when it was rendered).