If you noticed that when you place an image in your blog and roll over it in Internet Explorer you get alternate text displayed for several seconds, but when you try to do it in Firefox the text doesn't show up. This is because Firefox doesn't display Alt text like IE does.
This is quite strange but the fix is really easy. If you add a title attribute to an image then even Firefox will display it as an alternate text.
Blogger doesn't provide you with instant title attribute adding feature but it's really not difficult. Just insert image as you allways do by clicking on the Add Image button and then go to Edit Html mode. Locate where is the image tag and add the following line after src attribute:
title="some image title to display on roll over".
Your whole image tag would look like this:
<img id="..." style="FLOAT: right; MARGIN: 0px 0px 10px 10px" alt="you see alt text" title="you see title text" src="..." border="0" />
When you have only Alt attribute in the img tag then IE will display it but Firefox won't, when you have both Alt and Title attributes, then both browsers will display title attribute. Using title attributes with images can improve your blog or site in a way that it can be indexed better by search engines and Firefox users will see Alt text as well.
Bellow is two images working as examples:
This image has only Alt attribute (Alt="This is Alt text") , if you read this blog with Firefox you probably don't see when roll over
This image has both Alt and Title attributes. You should see roll over text on both IE and Firefox
Related: How to display Html code in Blogger