Embed JonDesign's SmoothGallery into your posts and pages.
If you're using the visual editor the div-tags may be replaced with p-tags. To keep the markup intact you should disable the visual editor if you'd like to edit a post/page that contains a SmoothGallery.
To do this, go to Users -> Your profile and uncheck "Use the visual editor when writing". Once you've saved and published the post/page you can activate the visual editor again - but make sure to disable it again if you want to change a post that contains a SmoothGallery.
SmoothGallery doesn't seem to work with Internet Explorer if you use Prototype on your site.
Read about a solution here. Basically you'll have to make sure that you don't use Prototype and SmoothGallery on the same site or at least embed the SmoothGallery inside an iFrame.
Read about this here.