Is there security on the Internet?

For the typical user the answer is most certainly no but it depends entirely on how you define "sent via the internet." If you connect to a web site using the standard http protocol then it is an unsecured connection. If you are using the https (SSL) connection then it is encrypted and gives some degree of security however there are man in the middle attacks that can defeat SSL connections.

If you are talking about sending email then there is no security as the message crosses the internet unless you encrypt it with something like PGP. You can have TLS encrypted connections between mail servers that will protect the message as it crosses the internet but once it is received by the mail server it is unprotected. Thus the network connection between your client and the mail server is not secure. The message can be sniffed off the network and read.

The same goes for your user name and passWord for a typical POP3 mail account (most ISP accounts), it can be sniffed off the network and stolen. So bottom line is for the most part information sent via the internet is not secure unless specific measures are taken to secure it.