The first question is extremely basic and a very simple google query such as: ASP.NET - How do I redirect to another page? would have garnered you the information you are looking for, so go and try that.
The second question, I believe, is related to FormsAuthentication. After you have validated the users credentials you can use this method:
FormsAuthentication.RedirectFromLoginPage(<usernam e>, <create persistant cookie: true|false>);
I am not sure what you are asking about for the Web Site Admin tool.
You CAN move and resize the ContentPlaceHolders as long as you are trying to do it from within your MasterPage. If you could move and resize Placeholders on child pages it would defeat the purpose of having a MasterPage in the first place.
Read this if you want to know how to get a correct reply for your question:
.: Wrox Technical Editor / Author :.
Wrox Books 24 x 7