Generally you don't need the vga kernel parameter anymore since nowadays KMS (kernel mode setting) is the default and usually sets the optimal screen resolution by itself.
The only case I know in which you need the vga kernel parameter is if you're using a Radeon video card with fglrx, since this driver still doesn't support KMS.
In this case you can find out the correct value for your card and monitor by setting vga=ask. When you have chosen the correct resolution you can change vga=ask to vga=<chosen value>. Keep in mind that it can take decimal and hexadecimal values. From the table you linked to you can set either vga=795 or vga=0x31b for getting 1280x1024-24. As far as I know vga=ask usually gives you the hexadecimal values.