just wanted to inquire that can Visas be stamped on the Observation Pages of the Passport? I called my Embassy for renewal of Passport, however, the Passport Officer commented that you still have Observation Pages left. This was pretty strange to me as i never heard that Visas can be stamped on the Observation Pages. Does anyone has this experience?
The standard for Passport documents is defined by the International Civil Aviation Organization (ICAO), which is a part of the United Nations.
The "Observations" page you are referring to, whilst standard (in some form or another) across most countries passport books, is actually NOT a part of the standard requirements for a passport, and as a result there is no standard answer as to whether it can be used for Visas/stamps or not.
As there is no standard for this page, it's location and text on the page will vary between countries.
Many countries do place wording on this page that it can not be used for visas/stamps. Other countries place the observation page well before the "visa" pages in the passport, strongly implying that it is not to be used for visas. (eg, my Australian passport has 3 pages of "Information Information" text between the observations page and the visa pages.
For some other countries, the Observations page does not meet the requirements dictated by ICAO for a "visa" page (which includes things such as the background of each page containing a different image).
As a result of these points, you will almost certainly find that many (probably most) countries will be unwilling to place a visa or stamp on the "Observations" page - even if the page itself doesn't state it can't be done. This is especially true for a full-page visa sticker where the sticker would cover the "Observations" heading and any other text on the page.