Endpoint Protection

I am unable block URL through SEPM firewall policies.
please help

First you ensure that Network Threat protection is installed in your all clients.
The follow this steps for blocking it
How to block all website and allow only certain websites using Network Threat Protection Firewall rule. 

Look at this article with screenshots
https://www-secure.symantec.com/connect/articles/how-block-internet-address-sep-manager-firewall-rule 

In SEPM go to Clients----> <The req. group>--->Policies (Right side)---->Location specific settings--->

Client User Interface Control Settings

and assure that is in server control mode or in mixed mode. Also keep your rule as first rule in the policy....

I try above solution but unable to block gmail.com

Try this

How to block/allow website access using the Symantec Endpoint Protection Manager custom Intrusion Prevention Signature policy
http://service1.symantec.com/support/ent-security.nsf/docid/2008070803545448

Restart the client and try once..
Also flush the dns.
Are you set it as the first rule?
You client is in server control mode?
Then in firewall policy right click on the rule in logging and select both write to packet log and write to  Traffic log and see anything is getting logged in the client..(In client GUI view logs--->network threat protection)

How to block and log websites? 

Dear arvind km i restarted the system but till now i able to access the google or gmail sites.I also tried through Intrusion Prevention Signature policy as Mr. prachand suggest me but issue is still same.

Which are the components of SEP you installed?

Blocking gmail via a firewall policy is going to be tricky.  Gmail.com just refers the users to a specific google.com/accunts url.  As such, I'm not sure you'll really be able to block gmail in this fashion.  You might be able to stop casual users from typing "gmail.com," but if they click a gmail link just about anywhere else, they're going to get in.  Also keep this in mind, thanks to a copyright dispute in a few countries, googlemail.com is completely equivalent to gmail.com.

Title: 'How to Restrict Users to Specific Web Sites by Creating Firewall Rules for Managed Clients'
Document ID: 2009012915443648
> Web URL: http://service1.symantec.com/support/ent-security.nsf/docid/2009012915443648?Open&seg=ent