Visual Studio JavaScript intellisense feature is very cool. But if you are adding JavaScript files to Master Pages with ResolveUrl method, you can not use intellisense feature in design time. Also you can use intellisense feature with different way. There is a sample code below.

In Master Page :

Updated - 03.11.2008 (Thanks to Visual Web Developer Team) The other way:

I found a Solution in this blog :

How to manually extend the evaluation period
When the initial 60-day evaluation period nears its end, you can run the Slmgr.vbs script to reset the evaluation period. To do this, follow these steps:
1.Click Start, and then click Command Prompt.
2.Type slmgr.vbs -dli, and then press ENTER to check the current status of your evaluation period.
3.To reset the evaluation period, type slmgr.vbs –rearm, and then press ENTER.
4.Restart the computer.
This resets the evaluation period to 60 days.

How to automate the extension of the evaluation period
You may want to set up a process that automatically resets the evaluation period every 60 days. One way to automate this process is by using the Task Scheduler. You can configure the Task Scheduler to run the Slmgr.vbs script and to restart the server at a particular time. To do this, follow these steps:
1.Click Start, point to Administrative Tools, and then click Task Scheduler.
2.Copy the following sample task to the server, and then save it as an .xml file. For example, you can save the file as Extend.xml. 

3.In the sample task, change the value of the following “UserID” tag to contain your domain and your alias:
<UserId>domain\alias</UserId>
4.In the Task Scheduler, click Import Task on the Action menu.
5.Click the sample task .xml file. For example, click Extend.xml.
6.Click Import.
7.Click the Triggers tab.
8.Click the One Time trigger, and then click Edit.
9.Change the start date of the task to a date just before the end of your current evaluation period.
10.Click OK, and then exit the Task Scheduler.
The Task Scheduler will now run the evaluation reset operation on the date that you specified.

MasterPages came with ASP.NET 2.0 and it's very useful. If you are using master pages, JavaScript files, images, links and sub folders in own projects. This article is very useful for you.

For example you insert image in your master page and create an aspx file in subfolder.

In master page : <img src="Images/mustafaozcanblog.png" alt="Mustafa ÖZCAN's Blog" />

Sample.aspx file is in samples folder and it is use master page in root folder. Added images cannot be displayed in rendered sample.aspx page because images folder in root folder but samples.aspx page search it in samples directory.

So you have two ways solution for this problem:

1st Way: You must change this line for added image  : 

<img src="~/Images/mustafaozcanblog.png" alt="Mustafa ÖZCAN's Blog" runat="server"/>

2nd Way: You must change this line for added image :

 <img src='<%=ResolveUrl("~/Images/mustafaozcanblog.png")%>' alt="Mustafa ÖZCAN's Blog" />

You can use 2nd Way to added JavaScript files and other external content in master page file.