Technology 
Bits and bobs I've learnt along the way:
When reaching a Web service from a remote machine through the browser you get the message "The test form is only available for requests from the local machine."
Simply enter the following into the Web.config file in the <system.web> section:
<webServices> <protocols> <add name="HttpPost"/> <add name="HttpGet"/> </protocols> </webServices>
When Internet Explorer 6 comes across a Web page which has a .png file in it that has a transparent background it will look bluey grey rather than transparent! IE7 has fixed the problem but in the mean time why not make them .gifs instead or use the AlphaImageLoader filter as suggested by Microsoft
http://support.microsoft.com/kb/294714
I recently received a call asking for help with installing a Web site in IIS. The client had Windows Server 2003 and IIS 6.0. They had installed a Web site developed in .NET 2.0 using a provided .msi file. When they went to the first .aspx page they got a Page Not Found 404 error. I checked the file name, security in IIS, file permissions on the virtual directory, all seemed fine. So, I checked the IIS error logs - no more clues in there.
After some searching I found the solution - they needed to go to IIS, Web Extensions directory and allow ASP.NET. By default, it is disabled in Windows 2003 in order to preserve security. Note: Web Extensions are new to IIS 6 so other versions, for example, IIS 5.1 won't have it.
If when trying to view your .aspx pages that are running on an IIS server, you get the message "Server Application Unavailable. The web application you are attempting to access on this web server is currently unavailable. Please hit the "Refresh" button in your web browser to retry your request." examine the security on your sites folder. Navigate to the folder which houses your files. Right click. Choose Properties and Security. Make sure the appropriate accounts have read access.
A customer recently installed an ASP.NET Web Service which I had developed and asked me why they were receiving this error when all the files were in place as expected. They were using IIS 6. To solve this is simple - make sure that under Web Service Extensions is "Enabled", not "Prohibited"