Back in March I wrote the following article: Dynamics CRM Developer Tip O’ the Day: Working with Tabs.

Today I was working on some pre-existing customer JavaScript and ran across this:

Xrm.Page.ui.tabs.get(0).sections.get(6).setVisible(false); // Hide section

Don’t ever do that! Bad developer! Bad!

So again, never, ever use the numerical value to reference a Tab or a Section, unless you have no choice. 

We don’t want to use numbers because if you move or add Tabs or Sections, your code will no longer work.

Do this instead:

Xrm.Page.ui.tabs.get("General").sections.get("Details").setVisible(false); // Hide section

As long as your Tabs and Sections are named properly, you should not have an issue.