Sharepoint Designer - Clear Cache

How to Clear Sharepoint Designer Cache

1. Exit Sharepoint Designer if it is open.
2. On the local computer, browse to the following folder:
   C:\Users\<username>\AppData\Local\Microsoft\WebsiteCache
   Note To locate some of the files and folders, you may have to configure File Explorer or Windows Explorer to show hidden files, folders, and drives. To do this, use one of the following methods.
   
   Windows 8
   Open File Explorer, tap or click the View tab, and then select Hidden items.
   Windows 7
   For more information about how to unhide hidden files or folders in Windows 7, see Show hidden files.

3. Delete all the files and folders that are present.
4. On the local computer, browse to the following folder:
   C:\Users\<username>\AppData\Roaming\Microsoft\SharePoint Designer\ProxyAssemblyCache
5. Delete all the files and folders that are present.
6. On the local computer, browse to the following folder:
   
   C:\Users\<username>\AppData\Roaming\Microsoft\Web Server Extensions\Cache
7. Delete all the files and folders that are present.
8. Start SharePoint Designer 2010/2013 and proceed with your work

Courtsey :- http://support.microsoft.com/kb/2794961

Powershell to make List column optional in Sharepoint

$web = Get-SPWeb -identity "http://siteurl"

$list = $web.Lists["ListName"]

$column = $list.Fields["Title"]

$column.Required = $false

$column.Update()

$list.Update()

$web.Dispose()