I have the following HTML as an example:

<script src="foo.js?v=1"></script>
<script src="foo.js?v=2"></script>
<script src="bar.js"></script>

Using the selector

^=

to retrieve the first two <script> elements I get inconsistent results in different browsers:

Firefox 3.5.9, Safari 4.0.5 and Chrome 5.0.342.9:

$("script[src^=foo\\\\.js]").length === 2 // true and correct according to docs
$("script[src^=foo.js]").length === 0   // true and correct according to docs

Internet Explorer 8.0.6001.18702:

$("script[src^=foo\\\\.js]").length === 2 // false!
$("script[src^=foo\\\\.js]").length === 0 // true
$("script[src^=foo.js]").length === 0   // false!
$("script[src^=foo.js]").length === 2   // true

This means: to get the correct results I have to use

$("script[src^=foo.js]")

for IExplore and

$("script[src^=foo\\\\.js]")

for the other browsers.