Lag. The time when your computer runs slowly. Well, here are some tips (beside upgrading your computer) to help relieve some of that lag.

Latency

Latency, often called internet lag or ping, is the time between information packets are sent and recieved between the server, and client (player). The higher your ping is, the more time it takes to deliver and recieve packets, which is bad.

You can sometimes decrease your ping by stopping any other downloads you have, or quitting any sort of non-critical internet using programs such as MSN, IRC, XFire, etc. What determines your ping is the distance from the server, and how (over)loaded are your computer, or the server's. (An example where the server itself would lag, if it is overwhelmed by a lot of players playing on it at a time, in client case it is caused by a lot of programs running at a time or using up the internet with another program than your browser.)

Packets are for doing a lot of things in the game: Sending information about where your character is in the game currently, so other players see where you are, it also sends info about when do you use your weapons, or the server sends some to make clients see incoming zombies, etc.

(Some players noticed that at the moment, players are often controlled by AI (Artificial Intelligence), which makes them do what they're supposed to be doing, but not in the exact same way that other player may be acting. Sometimes you can notice other players "teleport", in other words quickly move to another place. This is probably when you recieve a packet about where that other player is at the moment, although hopefully in the future there will be less AI and more precision, but that would probably make latency have more meaning to it.)

Browser

There are several to choose from, and some may work better for you than others. Opera, Firefox, and Internet Explorer are all fine choices.

If you use Firefox, a helpful tip would be to download IE Tab. It is an extension which lets you run selected pages with the IE engine instead, and it works pretty well. Changing between the two engines only requires one click as well.

Clear Cookies

Clear the most recent places you've visited. It is about the same on every browser, so go to:

Tools > Internet Options > Delete Cookies


That's for IE. Firefox is a bit easier with 'Clear Private Data'. WARNING! This will log you out of every program that is browser based, including forums, this wiki and many more.

Flash

First, uninstall Flash. This tool will remove all past versions of Flash from your computer. Then, install either Flash 9 (The lastest stable version) or the Flash 10 Beta. (Better performance, but problems in Multiplayer)
This should cover most lag problems.

Mouse Lag

In Windows you can fix this be going to:

Control Panel > Keyboard > Repeat Rate

Set it somewhere around the lower end of the scale.

Sound

Sound is a major contributor to lag - simply turn it off in the Inner City menu. Be aware though, that in most cases you hear the zombies sooner than you actually see them, so turning sounds off may lead to a disadvantage.