When I use Firefox everything is ok but there's huge lag with IE.

IE has a lot of issues, the least of which being RAM suck and spyware vulnerabilities. These can combine to cause a very slow browsing experience as well as a security hazard. IE is also non-standards compliant, so coding is wonky with it -.-;

Subeta hates IE. Just stick with Firefox IMO.

Because IE is absolute crap. Stay with firefox or any other browser that isn't IE and you should be fine.

Subeta was specifically coded for Firefox and Safari, because of that there are some big problems with IE, such as lags, parts of the site not working ect. ect. If you have the option to use Firefox for Subeta, just do so and it will be fine :)

I really do suggest to look into other browsers instead of IE, that one got more security holes than swiss cheese :3