Datagrid and back button

[Guest]

All,

I have a ASP 1.1 webform 1.aspx that has a datagrid and image button
control. The image button control retrieves a thumbnail image using another
webform b.aspx that gets the image from a SQL database via a dataset and
Response.BinaryWrite(xxxxx)).

If the user clicks on the thumbnail image in 1.aspx datagrid a larger size
is retrieved from the SQL DB and displayed via b.aspx

The problem I am experiencing is when the user clicks on the thumbnail image
to get the larger sized image and then clicks the back button in IE explorer
the thumbnail image is no longer shown but instead the larger image is - why
is this?

Why is the thumbnail image not in the history anymore?

Thanks
MSuk