Europe Online Advertising:
Spending Trends and the Target Audience
"Internet ad spending in the five largest nations in Western Europe—France, Germany, Italy, Spain, and the UK reached €1.9 billion in 2005. That represented a sizeable 38.2% gain over 2004's spending, according to BIPE/Groupe Interdeco/OMD [...]"
Yes, Europe is diverse and it potential and realization are different. Overall you could say, Europe is at least 2 years back to USA (and Germany even further) with some exceptions.
eMarketer says:
"The online ad market in Western Europe looks much like the US market in the early part of the decade—with two exceptions. First, paid search and rich media are more fully entrenched than they were in the US. Second, ..."

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Europe Online Advertising: Spending Trends and the Target Audience
By David Hallerman
February 2006, 23 Pages, 69 Charts, USD 695
About Germany see also:
Nielsen Media Research ermittelt ...