Multiple events on post-back

I am facing a unique problem (looks unique to me at least). I have a dropdown whose auto-postback is enabled. User can select a value from the dropdown to go to another page. But when the user comes back to original page by clicking the back button on the browser and clicks any button then on the post-back caused by the button, first the “SelectedIndexChanged” event handler of that dropdown is called then the “Click” event handler of this button is called. Hope I have explained the problem clearly.

Can anyone tell me what’s going wrong and how to solve the issue?