thanks, the problem was the resolution of monitor,the solution is edit
xorg.conf
sudo gedit /etc/X11/xorg.conf
Section "Device"
Identifier "Configured Video Device"
EndSection
Section "Monitor"
Identifier "Configured Monitor"
Vendorname "Generic LCD Display"
Modelname "LCD Panel 1440x900"
Horizsync 31.5-64.0
Vertrefresh 56.0 - 65.0
modeline "1440x900_60.00" 106.47 1440 1520 1672 1904 900 901 904 932 -HSync
+Vsync
Gamma 1.0
# modeline "640x480@60" 25.2 640 656 752 800 480 490 492 525 -vsync -hsync
# modeline "800x600@56" 36.0 800 824 896 1024 600 601 603 625 +hsync +vsync
# modeline "800x600@60" 40.0 800 840 968 1056 600 601 605 628 +hsync +vsync
# modeline "1024x768@60" 65.0 1024 1048 1184 1344 768 771 777 806 -vsync
-hsync
# modeline "1440x900_60.00" 106.47 1440 1520 1672 1904 900 901 904 932 -HSync
+Vsync
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
DefaultDepth 24
SubSection "Display"
Depth 1
Modes "1440x900"
EndSubSection
SubSection "Display"
Depth 4
Modes "1440x900"
EndSubSection
SubSection "Display"
Depth 8
Modes "1440x900"
EndSubSection
SubSection "Display"
Depth 15
Modes "1440x900"
EndSubSection
SubSection "Display"
Depth 16
Modes "1440x900"
EndSubSection
SubSection "Display"
Depth 24
Modes "1440x900"
EndSubSection
EndSection
reboot pc
thanks, i love trisquel
