Just a quick question: How do I avoid urlencoding an ampersand (the '&' character). I wish to make a URI with parameters - the parameters are separated by ampersands, but they get encoded automatically (i.e., '&' goes to '&'). 

The code looks like

<apex:iframe src="https://some-domain.com/action?a={!value1}&b={!value2}"/>

where value1 and value2 are attributes on my controller. The ampersand in between the two parameters is causing me trouble...

I would have expected that only application of the URLENCODE function would result in this substitution, but this is not the case. The '&' character is substituted without it.

All help is appreciated. Thank you!