32 bytes, ehr ... 9, ehr ... 7!!! to know if your browser is IE
Update another clever trick from comments, which I will explain later: if(!+"\v1") // true only in IE if("\v"=="v")// true only in IE try{IE=window=!1}catch(e){IE=!0} it works, doesn't it? The reason is simple, if we consider "\v" as a vertical space, browsers interpreter that check in this way: !(+ 1 ) where "not one" is always false, considering that 0 is always casted as false, and every other number is casted as true. Internet Explorer will ignore the vertical space, trying to cast a "v" character into a number, thanks to the sign (plus or minus, it does not matter) // How IE interpreters the code !(+"v") // where isNaN(+"v") === true // and where NaN is implicitly casted as false About conditional comments I read a lot of comments in both Ajaxian and other places ... well, guys, this is a trick as conditional comment is. The day IE will interpret correctly the "\v" character, Opera or so...