Prepare yourself for 2015 update 1

Whats new?
The new form rendering engine - The new form renderer was built to provide better performance. Forms will load significantly faster and more efficiently. The new renderer is based on previous generations and has the same functionality and behavior

In summary:

• Iframes are now kept throughout the user session
• Custom scripts are loaded in separate iframes
• No changes in supported scripts or form
  capabilities 

Examples of things that will break:

• Any attempt to access DOM in the content iframe using JS, jQuery or other 3^rd party libraries (document.getElementById() or jQuery selectors)
• Creating a new HTML content in the parent window for persistent content (and assumed that the parent window was the main CRM iframe.
• Window.load, parsing iframe/form URL
• Attempting to use unsupported (non-XRM) APIs, especially undocumented ones that may have been shipped with CRM for internal usage only
• Accessing window.parent() from a web resource that may assume for example there’s a variable set in the current window context. 

More detailed info here:
http://blogs.msdn.com/b/crm/archive/2015/04/29/microsoft-dynamics-crm-online-2015-update-1-new-form-rendering-engine.aspx


However there are some things that we need to do to ensure full compatibility when upgrading. So use the Custom Code Validation Tool, to validate your code before you update, use always a sandbox before you update the Production server.

Download here:
https://www.microsoft.com/en-us/download/details.aspx?id=45535