The Toshiba Satellite M305-S4907 Notebook PC, uses a single CCFL for a Backlight.
Primer before we go on;
An LCD screen cannot produce light. It needs an additional light source,http://solutions.3m.com/wps/portal/3M/en_US/NA_Optical/Systems/BehindTheScenes/Optics101/
Click on the monitor image.
The additional light source is a Backlight.
A Backlight can be a CCFL, (Or two of them), or a series of LED's.
(Light Emitting Diode)
A CCFL is a Cold Cathode Fluorescent Lamp.
Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.
Average thickness is 2mm. That is a little larger than 1/16th of an Inch.
Average length is almost as long, as the LCD screen is in height.http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/
View the last 8 photos.
A screen Inverter is used on laptops that use CCFL for Backlighting.
A screen Inverter converts the power (Electricity), from the laptop, for the LCD screen, and Backlight.
Laptops that use a series of LED's for backlighting, do Not use a screen Inverter.
90 PERCENT OF THE TIME the fault can be attributed to a bad screen Inverter.http://www.sparepartswarehouse.com/Toshiba,Satellite,M305-S4907,PSMD8U-02R015B,Laptop,Inverters.aspx
The plastic thin frame in front of the LCD screen, is the Display Bezel. (Toshiba = LCD Bezel)
The screen Inverter is located behind the Display Bezel, and mounted at the bottom of the LCD screen.
(LCD Screen Frame, actually)
Easy to get to; easy to replace.http://www.irisvista.com/tech/laptops/Toshiba-Satellite-M305/remove-screen-inverter-video-cable-1.htm
How to test a screen Inverter? Requires a Sensitive multimeter.
Read fairly expensive,http://www.fonerbooks.com/test.htm
Because of this; and the low cost, plus ease of replacing; most home users just opt to replace it.
Fluorescent lamps have MERCURY inside. HIGHLY poisonous.
Now couple that with the long thin makeup of the CCFL, and how easy it is to break it.
This is why if the screen Inverter is found to NOT be the problem; I would suggest replacing the LCD screen itself; instead of trying to replace the CCFL, and cause possible Mercury poisoning.
For additional questions please post in a Comment.