Hello,
I have a trouble with my laptop´s display 15.4” WSXGA+ with resolution 1680x1050 (16:10).

Size ratio should be 16:10, but my fedora 6 thinks that it is display with 4:3 ratio and the screen is stretched in the horizontal direction.

And the next trouble is that I dont know the brand of TFT display. Linux identified the screen as generic LCD 1680x1050

Kernel version: 2.6.18-1.2849.fc6

Output of xorg.conf

# Xorg configuration created by system-config-display

Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Synaptics" "CorePointer"
EndSection

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "cz"
Option "XkbVariant" "qwerty"
EndSection

Section "InputDevice"
Identifier "Synaptics"
Driver "synaptics"
Option "Device" "/dev/input/mice"
Option "Protocol" "auto-dev"
Option "Emulate3Buttons" "yes"
EndSection

Section "Monitor"

### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
Identifier "Monitor0"
ModelName "LCD Panel 1680x1050"
### Comment all HorizSync and VertSync values to use DDC:
HorizSync 31.5 - 90.0
VertRefresh 59.9 - 60.1
Option "dpms"
EndSection

Section "Device"
Identifier "Videocard0"
Driver "i810"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
Modes "1280x1024" "1280x960" "1280x800" "1152x864" "1152x768" "1024x768" "800x600" "640x480"
EndSubSection
EndSection

It's a common problem having a widescreen display that's stretched; there are some how-tos on the web (I just read one talking about Acer WLMi screens) that might help you out. You'll need to make sure the vertrefresh and horizsync values are correct, and try out which resolution works; not all 16:10 resolutions might work. I've also encountered a problem where a shared video memory, though "big enough", caused me to be unable to watch DVD-movies on the laptop (they were sluggish) when using a correct widescreen resolution, I could only play them when I switched to a non-widescreen resolution.

The Acer-laptop guide I saw yesterday (found from Google) had some good points in it, try to hunt it down. I don't remember the search terms (sorry) I used, but I'm pretty confident you'll find either it or some other how-to/guide/help page about this problem.

X just likes to not use widescreen resolutions, unless forced to.

My first step would be to add the resolution to the modes line (close to the end of the config that ou posted). If you don't tell X that it can use it, it will not use it.
Another thing I notice is the videocard driver. Not sure if the i810 driver supports the 1680x1050 resolution.