Page not getting loaded with AJAX effects .net

Dear all,

              I have developed asp.net application . On Login page i have used <asp:TextBoxWatermarkExtender ></asp:TextBoxWatermarkExtender >

for "user name" and "Password" . Now the problem is , when page gets loaded it does not load "ajax" properly. It does not give any error

but to see "ajax" effect i need to press F5 many times. What should i do to overcome this?

Any one can help?

Thanks in advance.