This is normal - it does not represent the signal strength, but only whether it's active or not. (There's also an animation when it's attempting to connect to a WiFi network)
This behavior was changed in the Windows Phone 8.1.
Now the WiFi signal on top of screen shows the power strength as in the WiFi settings menu.
Simply swipe the toast notification to the right and it will leave your screen. If you have multiple pending toast notifications (for instance, if you receive multiple texts concurrently), you will have to swipe each of them in turn. However, this will dismiss them. You don't even have to unlock the phone.
In portrait mode, the system tray (including the clock) will show while either the SIP/keyboard is visible or the menu is expanded. I'm not aware of any way to show the system tray all the time.
It's not possible to show the clock at all in landscape mode.
It will always be full when connected, regardless of signal strength.
Here is a break down of the three Wi-Fi related icons in the status bar (full list of status icons):
Connected to a Wi-Fi network. The icon is animated when your phone is trying to connect to a Wi-Fi network.
Wi-Fi is turned on, but your phone isn't connected to a Wi-Fi network.
You can make the icons appear temporarily by swiping your finger down from the top of the screen. To my knowledge, there's no way to force them to remain down all the time.
However, this does not work in applications that have chosen to hide the tray entirely such as Facebook, Twitter and Internet Explorer.
(FYI, pre-Mango the system tray colour could not ...
I would go with Richards answer.
Just press the three dots at the right bottom corner and the clock will appear.
A quick tip that I use myself is to just start dragging the three dots, as soon as you start moving them the clock will appear. That way you can quickly show the clock without hiding the webpage itself :)