Please you should ask the question correctly. The event whether javascript or codebehind(c#,vb.net).
code is below
for codebehind
protected void btnSave_Click(object sender, EventArgs e)
{
}
for javascript
<a href="http://www.codeproject.com" onClick="window.open('http://www.codeproject.com');return false;">Code Project</a>
please let me know if you have any doubt