When L4D was released back in November of 2008, a lot of PC users were looking for the in-game browser. It turns out that L4D did not have the in-game browser enabled by default unlike other games by Valve that has multi-player e.g. Team Fortress 2. This turned out to be a huge burden for people that have their own servers because well, let's put it this way...they want to play on their 'own' server. And with L4D's matchmaking system it's either a hit or miss. So what do we do then? Simple. Enable it.

Enabling Through 'Set launch options...'

This is probably the easiest way to enable your in-game browser permanently in L4D. What you need to do first is open Steam and then go to your My games tab and right-click on Left 4 Dead. Select Properties and then click on Set launch options....

After that just type -serverbrowser and click Close. You're done! Start L4D to double-check.

Now you may notice one thing here, you can't see the Steam group servers unlike when the server browser is disabled. So my take on this one is only use this one if you don't belong to any Steam group and you just want a quick and fast way to connect to L4D game servers.