Why does Steam sometimes not connect?

[Jango]

I am getting very irritated at Steam because sometimes it can't seem to connect to Online mode, especially now that if it happens I can't play Modern Warfare 2...

When I boot the computer up, it says that Steam cannot connect to the online. Then when I try to startup a Steam game nothing happens for ten seconds then it says 'Steam is updating' and no matter how long I leave it, nothing happens.

Please does someone have a solution to this problem?

Thanks in advance.

 

[Jango]

My client is not behind, because most of the time Steam actually does work perfectly.

It's just that sometimes Steam won't connect atall...

 

[Jango]

My download speed is 893kbps and my upload speed is 976kbps. (Measured by 'Aduit my PC' Broadband speed test).