Cannot connect web application to a server I get A network-related or instance-specific error

I am building a web application so I want to connect the web application on local machine to a company server. When copying the connection string from the same web application sitting on the server to my local web config I get the following error "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)". Your help will be appreciated....