Connection to steam is lost

[TheDylanator]

When i try to join a game with friends or make one i will get a loading page that will load to 10 percent then do nothing after about 5minutes of it doing nothing...
It'll eventually come up 'connection to steam was lost' when this happens my steam connection will constantly drop but if i close down l4d it will work perfectly but i wont be able to join any games of any kind for a few hours.
Incase your wondering i can join online games perfectly fine unless i join a friend game first.