Password strength checker
You can replace all of the 

if(x.match(...))
    return true;
else
    return false;


with:

return x.match(...) !== null;


or if you're content with returning a truthy/falsy value instead of proper booleans you can even simplify it to: 

return x.match(...)

IsEnoughLength is ungrammatical. I'd use IsLongEnough
You're mixing the password strength estimation with presentation logic. You should have one function which returns a value indicating the strength of the password and another which manipulates the DOM.
Use CSS classes to format the text instead of &lt;b&gt; and &lt;font style=
Personally I wouldn't bother with argument checking in such a simple internal function. But if you do, throw an exception on programmer error, don't just return false.

if ((str == null) || isNaN(length))
    return false;


should be something like

if (str == null)
    throw new Error("str must not be null");
if(isNaN(length))
    throw new Error("length must be a number");


(or a fancier exception class if you want)