Hello.
<snip - do not link to hacking sites>
Their layout, the content container is not 960px like most of the web sites right? if yes, is it common with mybb templates? what is the suggested width grid size?
Thanks!
That forum uses a percentage, so it will scale to the 85% of your browsers width.
960px is fine, but far from what most websites use. It's generally the most compatible fixed-width for a variety of resolutions/monitor sizes.
It depends on your target audience. If you're making a forum for a group that generally has higher-end computers (and thus larger resolutions), you can get away with making your theme wider if you want. You don't have to conform to some notion that there is a be all and end all width for websites. Find out what is most appropriate and go for it.
Of course these days many people will also browse on their phones/tablets, so a mobile theme doesn't hurt - but it's also not necessary.