OT: Script question

I have the following code that works to a point: // discover if browser is crappy Opera or crappy Safari str=navigator.userAgent; // Agent is unique for our purposes var sf=str.indexOf("Safari"); // found if browser is Chrome or Safari var ch=str.indexOf("Chrome"); // not found if browser is Safari var op=str.indexOf("Opera"); // unique for Opera var opt=1; // alternate shown below but not used ovar=window.opera; // is undefined if browser is not Opera if (!ovar) { opt=-1; } // unique for Opera // Safari gives sf=91,ch=-1; Opera gives sf=-1,op=7; Chrome gives sf=-1,ch>0. // Jump to different markup if crappy browser if (sf>0 && ch=0) { window.location.replace('Mobile.html'); } // ** NOTE treat crap as if mobile phone ** // Code is a one-pager; there are mobile phones that struggle and die with // message "Page too large" "open media site"

var isIE=str.indexOf("IE"); // not found in other browsers if (isIE>0) { window.location.replace('PCbase.html'); } var isMozilla=str.indexOf("Mozilla"); // Presumes in all variants; includes Netscape if (isMozilla>=0) { window.location.replace('PCbase.html'); } if (ch>=0) { window.location.replace('PCbase.html'); } // for Chrome

document.write(str+""); document.write("At this point, browser is not Safari, Chrome, Opera or IE or Mozilla"+""); // So, ASSuME we have mobile phone browser // window.location.replace('Mobile.html'); // -----^ always executes; previous valid .replace somehow bypassed

If i un-comment that last window.location.replace line, the proper execution of going to PCbase.html fails, and i get Mobile.html instead.

How can this be fixed?