>>>>>>I am trying to incorporate into my project a masked input plug-in (URL: http://digitalbush.com/projects/masked-input-plugin/)
>>>>>>
>>>>>>When I add this .js
>>>>>>

>>>>>><script src="Scripts/jquery-1.7.1.js" type="text/javascript"></script>
>>>>>><script src="Scripts/jquery.maskedinput-1.2.2.min.js" type="text/javascript"></script>
>>>>>>

>>>>>>to a separate .aspx file in my project, the mask() function works very well.
>>>>>>
>>>>>>But when I add it to a page that uses Master page, I get error:
>>>>>>

>>>>>>0x800a01b6 - Microsoft JScript runtime error: Object doesn't support property or method 'mask'
>>>>>>

>>>>>>
>>>>>>The test code is identical in separate test page and the page that uses master page:
>>>>>>
>>>>>>

>>>>>> <script type="text/javascript">
>>>>>>        $(document).ready(function () {
>>>>>>             $("#txtPhoneNumber").mask("(999) 9999-9999");
>>>>>>        })
>>>>>>    </script>
>>>>>>

>>>>>>
>>>>>>The error (above) happens on the line .mask() above.
>>>>>>
>>>>>>How would you recommend to debug this situation? TIA
>>>>>
>>>>>Do you have both scripts included into the master page ? (jQuery and plug-in)?
>>>>
>>>>Yes, I have both scripts in the master page. And I also tried to add these scripts on a page where I use them. But to no avail.
>>>
>>>Make sure they are included in the right order and also try refreshing everything. I think I had similar problems when one of the scripts was not correctly loaded.
>>
>>I did double check this.
>
>Check the network tab in the debugger I just told you about and see if there is an error loading the js files.

This is helpful. The strange thing is in the Network tab I see the maskedinput.js is being loaded. But somehow, after it, the jquery-ui.js is being loaded. But I don't have the script (in my master or pages) to load the jquery-ui.js. Althought the jquery-ui.js is on the disk. So maybe all .js libraries are being loaded automatically. I will try to temporarily delete jquery-ui.js to see if it makes the difference.