>>>Why sometimes pressing key tab on form with pageframe the focus goes to another page. How to avoid this?
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>>When you press a tab, the corresponding page will get focus by default. If that does not happen to you, you must have added code which overrides the default behavior.
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>Which method must I use to avoid that the cursor goes to another page?

Do you mean that you do NOT want the page to change when someone presses a tab?