while debugging some javascript i have come to see that TexMate has an issue with the CSS selector, border-width written in Javascript as style.borderWidth

If i write style.backgroundColor, it will show in color green in Textmate.

I have retained the TextMate default color scheme in preferences/fonts colors/Mac classic.

when i write style.borderWidth it stays black as if it were a variable.

I would assume the Browser compiler or interpreter engine ? would accept the Javascript script as is, and that TextMate would not be adding any encoding to its interpretation of the script while showing style.borderWidth as invalid. 

i am learning javascript from a book and the author is not ordained by thy holy one and this script works to some degree, yet is off balance, this is what i am working on.
var d1 = document.getElementById("div1");
var d2 = document.getElementById("div2");

d1.onmouseover = function()
d1.style.backgroundColor = "00ff00";
d2.style.borderWidth = "7px";

d1.onmouseout = function()
d1.style.backgroundColor = "#ffffff";
d2.style.borderWidth = "1px";
I have composed this message offline going over the message many times to see that it is concise and to the point, forgive me if it is long winded and confusing.
Thank you