if you don't need xorg, use the xvesa version:

http://mirror.slitaz.org/iso/3.0/flavors/slitaz-3.0-xvesa.iso

Hi @Slavax -- you could try the 'tazx' tool to set your driver and hopefully resolution.

It is the same thing also with vesa: xrandr tell me that I have only two resolutions, 640x480 and 800x600.
How add 1024x768???

Iis the same thing also with tazx. It lists only the two above resolutions with deph 15,16 and 24.
How add 1024x768?

http://doc.slitaz.org/en:guides:xorg-xvesa

If you're using the vesa driver but have an ati or nvidia card the easiest way may be to install one of those drivers. Slitaz can do this for you, launch "Hardware detection and drivers" from the "System Tools" section of the menu. There is a "Install non-free packages" check box that you may want to uncheck if it is checked. That way you will get the community developed version. These drivers will usually give you higher resolution if your card is capable.

If you want to continue using the vesa driver and your monitor is lcd you may have to fool the driver by providing Horizsync. It's bogus because lcd doesn't need it but evidently the vesa driver does.

This worked for me on an old laptop:
Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
HorizSync 30.0 - 83.0
Modeline "1024x768_60.00" 64.11 1024 1080 1184 1344 768 769 772 795 -HSync +Vsync

For each entry in the screen section add or modify the modes:
Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
SubSection "Display"
Viewport 0 0
Depth 1
Modes "1024x768"

Before making your changes you may want to backup your xorg.conf. If your changes don't work you can remove the edited file and restore the old one. Use the following commands:
rm /etc/X11/xorg.conf
cp /etc/X11/xorg.conf.back xorg.conf

Xvesa -listomodes lists only 640x460 and 800x600.
Let me just make a little resumé.
I have downloaded Slitaz. I have read that I need to modify xorg.conf. I have done it, no result. Somebody told me to download xvesa flavour. I have done it, no result.
(by the way, I do not know the menaing of xvesa and xorg, but go ahead)
Now it is suggested to me a link which says that xvesa is useless, and for xorg indicates the change to xorg.conf I have already made.
Plase be patient because I am a newbie, but really I do not understand all your contractdictory suggestions.
Thank you.

Thanks for your patience!

(This is similar to what Mark60 said; I was typing as they posted!)
With XOrg (or, just X) You add resolutions (or try to) using a ModeLine in the Monitor section. There is a generator:
http://xtiming.sourceforge.net/cgi-bin/xtiming.pl
in to which you need to type you monitor specs and required resolution.

This will generate a modeline; paste this in to the Monitor section and the related name (what is in quotation marks) as a Mode in the Display section.

Further:
http://www.x.org/wiki/FAQVideoModes (explanation)
http://en.gentoo-wiki.com/wiki/X.Org/Modelines (condensed)

=====

BTW, XVesa and XOrg (X) are graphics servers; they control your graphical output. XOrg is bigger, has drivers etc. but isn't as simple to operate, whereas XVesa only uses the generic VESA driver and doesn't have (m)any config options. When it works, XVesa is great as it "just works" but with XOrg a lot more is possible. XVesa is being phased out for XOrg.

Hi Slavax,
Can you please run the following command and post the result.
lspci | grep VGA
That will help by letting us know the graphics chip you are using.

I would recommend using the Xorg server. If you choose to use it please post your xorg.conf so that we may make some suggestions.

I have tried to generate a modeline but then the X graphic server didn't start anymore. I had to rebuild xorg.conf with tazx, making some attempts because I do not know which driver I have to choose!!!!! :(((((((((

lspci | grep VGA gives the following output:

01:00.0 VGA compatible controller: Matrox Graphics, Inc. MGA G400/G450 (rev 04)

Is this information useful?
Many thanks.

Very!

Do you have the 'mga' driver in the list? That's the Matrox one. You may have luck with vesa if not, I can't rememeber if it worked with my MGA G200 card... though that had borked memory chips so probably not!
(Edit: ftp://ftp.matrox.com/pub/mga/archive/linux/2006/readme-mga-4.4.0.txt says yes!)

Ref: http://linux.die.net/man/4/mga

Ok, solved repeating tazx and then choosing mga as driver. Thanks to all you guys.