To turn off this feature in Internet Explorer: Select "Internet Options" from the "Tools" menu, of Internet Explorer. From the "Internet Options" window, select the "Advanced" Tab. Under "Multimedia", make sure that the "Enable Automatic Image Resizing" option is not checked.
To turn off this feature in FireFox: Select Options from the Tools menu to open the Options dialog. In the Options dialog, select the advanced tab. Select the general tab. Uncheck "Resize Large image to fit in the browser window"