undefined - more verbose info?

misc_modalWin = window.open(sUrl, sName, sFeatures);

after this line, misc_modalWin is undefined.

But I am not sure why.

From the Chrome debugger console:

sUrl
"../ds_dialog_small.aspx?ErrMsg=0%20events%20are%20assigned%20to%20Al%20Kramer%20-%20All%20Events&dlgType=1&lbl=Customer%20Reassignment%20Count"

sName
"_blank_1453153757664"

sFeatures
"Width=320px,Height=255px,Help=no,Status=no;Scroll=no"



Is it possible to "step into" the call for window.open(  )    ?  How can I get more information?