>>Don't know how you are checking the height but that's not true. The height of #Footer remains the same (101px) whether position is relative or absolute.
>>What changes is the height of the #Holder which (on my display) is 978px for #Footer position:absolute and 1079px when #Footer position:relative - i.e. the difference in #Footer height (1079-978= 101).
>>
>>Tested on Chrome/ Chrome Canary and Firefox but not IE. All of the above behaviour is what would be expected following HTML layout rules.
>>
>>What are you trying to achieve ?
>
>See the first image. The blue area is 102 pixels. When the footer is changed to relative, you can see, in image #2, that the footer is much bigger.

No. Don't know how you are highlighting that but you are covering the footer AND the body bottom padding.

See my two attachments from IE (using Dev Tools highlighting). First is the body (padding in pink), second is the footer. Sorry, slightly different scale....

Removing the body padding-bottom may give you what you need ?