Template Question

Hello,

I have edited template to run PunBB on my site within my site header. I have tables and Java Script using on my site header. Anyway I just edited templates and works fine with IE. But I have problem with other browsers like Opera, Netscape, Firefox, etc... my tables are displayed improperly. Of course I have edited main.tpl, admin.tpl, etc.

Then I've looked into details and try remove this:-

Then all browsers works fine with my header setting.

As I am not a experienced programmer, I don't know wheter this code is somehow important. Would you kindly advise whether it is alright for me to do this?

Thanks and appreciated.