Your IPS signatures have errors:
rule tcp, dest=(80,8080), msg="Accessing Google Website", content=www.google.com
rule tcp, dest=(80,8080), msg="Accessing Google Website", content=www.google.*
The content part must be surrounded by "", e.g. content="www.google.com". Asterisks don't work with the content keyword, you have to use the regexp keyword. See the SEPM online help for its dreadful syntax.
I would not use custom IPS signatures for blocking web sites. With your approach, you are blocking all data packages with the content "www.google.de" (including this very site 
).
Your firewall rule is perfectly fine and working in my test environment.
Please check your User Control Level (Clients > [Group] > Policies > Location-specific settings > Client User Interface Control Settings):
- Client Control means your SEP client ignores the SEPM firewall rule and uses its own one.
- Mixed control means your SEP client uses firewall rules in following order: SEPM rules above blue line in firewall rules form, SEP client rules, SEPM rules below blue line.
- Server Control means that your SEP client only uses SEPM firewall rules.
If required, switch to Server Control and try again.
And as Pete says, check if SEPM policy is applied on the client. Compare the policy serial numbers of the SEPM and the client (Help > Troubleshooting).