Some help with dropdown menus

Hi, I have just joined the forum and I need help with Javascrip dropdown menus. I have written a function which should change the background image of a button when it is clicked:

function change(el)
{

if (el.style.background='url(arrow-up-title2.jpg)'){
el.style.background='url(arrow-down-title2.jpg)'
}

if (el.style.background='url(arrow-down-title2.jpg)'){
el.style.background='url(arrow-up-title2.jpg)'
}


}


The problem is the background only changes once. When I click on the main menu the background is originally arrow-down-title2.jpg and this changes to arrow-up-title2.jpg but when I click the menu again it does not change back to arrow-down-title2.jpg.

Does anyone have an idea why?

This is how I pass my parameter:

<div id="menu" onclick="change(this);SwitchMenu('sub1')">Menu</div>

re: Some help with dropdown menus

Question moved to Javascript forum.

re: Some help with dropdown menus

re: Some help with dropdown menus

Wow, it works. Thank you so much !!!!!!!!!!!!!!!!!!!!!!!!!!!