Can I write two onclick ?
<input onclick="return confirm('&#199;ıkmak istiyormusunuz ')" onclick="window.location='logout.asp';"
Code:
 
<input onclick="return confirm('&#199;ıkmak istiyormusunuz ')" onclick="window.location='logout.asp';" type="button" value="&#199;ıkış" style="cursor:hand; background='#efefef';" onmouseover="this.style.background='#ffffff';" onmouseout="this.style.background='#efefef';" name="uyemiz_logout">&nbsp; &nbsp; &nbsp;</td>