I’ve been able to narrow down my problem with IE7b2 and background sprites. However, I still have not been able to create a stripped down test page that consistently mis-behaves. So my observations, while not scientific, could save you some hours of debugging.
Internet Explorer 7beta2 is not treating transparent png background images correctly. It sees “background-position: 0 0” as “background-position: 0 100%”. Come to think of it, I have only tried a vertical sprite, this may be the same for a horizontal sprite.
What’s the solution?
You could create a series of rules in your IE7 style sheet to measure your new sprites from the bottom up, instead of top down. But this doesn’t solve some of the other odd issues with IE7 and transparent png images. I’ve seen the images load upside down and I’ve seen the images move when you scroll the page and the image hits the bottom of the browser. I thought I was going crazy or that I had some sort of mutated version. But this pseudo-animation works on other computers.
Our IE6 style sheet replaces our pretty alpha transparent png graphics with a simpler index transparent gif version. We replaced our re-measured rules in the IE7 with this set and it has solved our problems. It would be great to take advantage of IE7’s ability to use alpha transparent png images, but this bug is just driving me nuts. I’ve also been in contact with the IE7 team. They are dedicated to building the best browser possible within their constraints and hopefully this will be figured out before the final launch of IE7.
One other note of advice. Creating alpha transparent png images via the save as command in Photoshop on a Mac gave us the worst results. Those images did some very funky things on the page. Fireworks created better images.
I don’t know if it is official or not, but I can say that the Microsoft engineers are interested in what developers have to say and have worked on this bug. I believe it has been fixed and will be all good to go with the final release of IE7. I can’t confirm or deny this, but I am pleased with their response to my initial post and followup.
Debugging IE7beta can become tedious when you need to continualy install, reboot, uninstall, reboot, etc to switch between IE6 and IE7b2 for testing. Jon Galloway has created a great method to run IE7 as a self contained browser. This will save you many hours in rebooting to test between the browsers. I’ve been using it for a week and can’t believe how easy this is to use.
A note of warning
You should only use this if you have a backup computer or are comfortable working with the registry. I found this out the hard way as the computer crashed while operating the standalone version of IE7. My laptop now displays very odd behavior with IE6. Another person on our team is experiencing similar behaviors. We’ll need to modify our registry tomorrow to fix this. How odd…? When you type an address in IE6, it opens firefox in a new window. It’s also ignoring conditional comments. Happy, Happy.
Firebug will soon join the web developer toolbar as a can’t-live-without tool in your browser. This Firefox extension lets you track down the JS, CSS, and HTML errors that are driving you crazy. Joe Hewitt just released the latest version of Firebug. Get it now while the going is good.
How good is IE7? I was wondering about that today as I reloaded it to do another batch of bug fixing. The proof may be in your CSS pudding.
We are using conditional comments to import either ie6.css or ie7.css to control our hacks.
So far, the ie6 style sheet is 342 lines long, including lots of whitespace and comments. A good portion of that is for re-assigning gif background images instead of png. The rest is an assortment of invoking hasLayout, box model changes, and the ever-popular z-index bugs.
I copied this style sheet, commented everything out and began re-introducing the rules to build the IE7 style sheet. I ditched the gif and z-index hacks. The most common hacks are for hasLayout and double-margin float. I’m still using a set of hacks to re-configure my background images that are being measured from the bottom up.
So, how big is the IE7 style sheet? Right now, we are looking at 146 lines of code, including white space and comments. That’s still a hefty amount and I’m not done fixing bugs. Yes, IE7 is much better than IE6, but still a far cry from the others.
I came across an issue with Internet Explorer 7 beta displaying the rating stars incorrectly in Yahoo! Tech. After doing some testing, I realized the browser was measuring the sprite image from the bottom up, rather than the top down. This is a significant issue. I had to create a new set of rules in the IE7 style sheet for the new measurements.
I use sprites extensively. I love the way they save server requests and I think they are much easier to maintain. The thought of fixing all of my sprites was enough to send me downstairs for another coffee. But I noticed the only sprites being affected were the ratings. I needed to find what was special about these. The ratings sprites use a span that is absolutely positioned in either an unordered list or definition list. This gives us flexibility for displaying them across the site.
IE7 Does it Right!
I created a test page for using sprites. I stripped the CSS down to simple list handling, floating, positioning, and sprite. IE7 handled it perfectly. I even replaced the links with spans and that still didn’t trip up IE7. Take a look at the test page , IE7 Sprite Test, to see the results. While I’m still having problems with IE7’s handling of sprites. I believe it is a unique combination of styles that is causing this issue. I don’t think the average person will need to worry about this.
When I do figure out what is going on with Yahoo! Tech’s rating sprites, I’ll update this blog with the solution. For more information on using sprites, visit Dave Shea’s article CSS Sprites: Image Slicing’s Kiss of Death on A List Apart.