Hey Firefox yea!!!
One of the problems with pages and Firefox is because Firefox is a better browser. Yea, that sounds like a paradox, it is.
The code that browsers read is called HTML. There is an organization that sets standards for HTML, how it should be written, and how browsers are supposed to display all the elements of a page.
Way back in the beginning when IE was battling it out with Netscape both companies would add features to their browsers that web creators could use for fancier things on their pages... but of course these extra features had nothing to do with the standards created for HTML and so a page written for IE might have features that would not display correctly in Netscape.
As time passed, IE became by far the most used browser. The biggest problem with it is that there is still a TON of non-standard compliant stuff in IE. Which means when a page is written according to the HTML standards, it won't display correctly in IE, and since most people use IE, web designers will write their pages to look the way they want them to, which "breaks" them in other browsers.
Good web designers use a lot of tricks and workarounds to make their pages display correctly in all browsers on both PC and Mac. Sometimes it can be quite difficult. A non-lazy web designer also has to take into consideration that some people with vision problems will want to increase the type size of the text, which will also "break" the layout if the page isn't designed correctly. Other lazybones create their pages in such a way that the type size
can't be changed, which just makes the page unreadable for people with vision problems.
There are also people who use audio browsers... the browser reads the page to them instead of displaying it visually. A good page is designed so that when it is read by one of those browsers, everything gets read in the proper order so that the page makes sense, there are good text descriptions of all of the images on the page, and a clear order to the links so that they are usable to someone who can't see and only uses a reader.
Yes it is complicated.
To make things even WORSE... IE has become more and more standards compliant over time. But of course then IE can't even display the pages properly for sites that were written to work around the bugs of older versions. If you look at the "source code" for any web page, near the top you will see a "doc-type" or document type. One of the specifications in that line can tell the newer, more "correct" versions of IE to actually simulate the errors of the older versions... so that older coded pages with display properly. This is called "quirks mode" and such a page tells IE to operate in "quirks mode" so that all of the errors will go back in place. In "standards" mode IE is supposed to display things in a more standards-compliant way.
There is a good example of how screwed up IE is... it is at :
Complex Spiral Demo
If you view this page in a standards-compliant browser, you will see some neat effects, including some semi-transparent areas for the menu on the left that move over an image that remains stationary as you scroll up and down. The cool thing about this page is that it uses ONLY standard HTML to create those effects... that is, there is no JAVA programming, Flash movies, or any other "add-ons" to get it to display that way.
If you look at the page in IE however, you won't see what the page is supposed to look like.
The page uses "style sheets" which are a relatively newer addition to the HTML standard... this way of creating a page is much more flexible for designers but the code standards for using these style sheets are all over the map with different browsers. One of the big debates right now is how much of this new coding to use, since it is more technically advanced, but then again if it won't work in common browsers... well its all a mess.
But you'll notice on the Spiral Demo... if you are using Firefox, on the bottom left of the browser window, in the status bar, all the way to the left is a little icon with a letter "A" in it. If you click on that, you will see a list of style sheets that the site creator has set up. You can choose one of the different styles and see how the page changes. This is a sort of frivolous example, but a practical web page could offer a style sheet with a larger type size that includes an easier to read font... a stylesheet that gives more contrast to the page so some will find it easier to read... in general the technology allows you to design the layout of the page separately from the content of the page and that's what makes it so powerful. Well, if it worked correctly.
The whole web thing is a mess, frustrating for people trying to design attractive and useful webpages that everyone can read.
Its getting better though. The next version of IE is supposed to be fully compliant with the way style sheets are read, the current IE still has a lot of bugs in that area.