You need to have a clear picture of what are you doing so you can understand what is happening. You were adding completely new web part zone to home page if I'm right, so now you are missing that zone and to start over you need reset the personalization for that page. Please do this in the MonoX administration and proceed. I'll get the design team to answer you if this is the right way to add new things. Regards

Ok so how I can reset the personalization for a page in administration side ? please guide me ?

Go to portal administration area and click on pages. Then right click a page from the list and choose option 'Manage web parts'. The popup contains a link to reset all personalization data.
Regards

This means any changes in the code in any page, I will have to do this ?

I would deeply appreciate if you could explain in detail in what situations I have to do this or do not have to do this for any page ?

You can reset dynamically added web parts and properties which were changed in administration. This is not related to code. Everything you have done trough administration panel will be reverted. Code changes remain.

This is how ASP.NET personalization works. The functionality you are asking for would require additional complexity (parsing the code of the ASP.NET page to see if there are any changes to Web part zones, and than going to the database to reflect those changes), which would in turn seriously affect the performance. Zones are being manipulated by site admins, and in my opinion this is small cost to pay for the flexibility and perfomance you get.

You are adding or removing MonoX building blocks so if you do such thing you will get an error. Do not mix this with adding web parts to zones MonoX will handle those scenarios very well but adding or removing core elements are tricky to handle. So only in that case you will have to reset personalization. Regards