In searching around for solutions to the back button problem, I came across quite a useful article which discusses various approaches to this problem.

Too often web application designers attempt to disable the back
button, or simply refuse to support users who use or rely on the back
button.

It doesn’t have to be that way. Disabling the back button is ultimately
impossible; it is far better to design for and live with the back
button.

Well there are actually some nice hacks for totally disabling the backbutton, but the author is right, this is not an advisable solution.

There are three common problems
associated with the back button in a web application.
It’s helpful to identify which of these problems you are trying to solve:

• ‘Warning: Page has Expired‘ errors when users
  click ‘back’
• Obsolete data is displayed when users click
  ‘back’
• Duplicate submissions occur when old forms are redisplayed.

It is important to clarify when it is appropriate to use GET and when POST, many developers pick and choose to suit their fancy but there are right and wrong reasons for each.

Where possible, GET requests should be used instead to perform read-only operations, like listing
information, displaying search results, showing menus, or executing reports.

These operations are normally
‘idempotent’ – if you carry out a read operation twice (for example by refreshing) no change
occurs.

Read the article for the full story.