Will they really notice it?
'The use of scrolling text is counterproductive - many users don't notice it at all, and those that do are frustrated by it.' (Safalra (Stephen Morley), 2003)
During 2000/2001, I tested a website with a scrolling marquee during my tutorial "Introduction to Web Usability Testing". It got different reactions in different countries. The North Americans simply blanked out the scrolling text. It was invisible to them. The phenomenon has become known as 'banner blindness' because it has been frequently observed during tests of e-commerce sites (for example Benway and Lane, 1998). Anything that looks like an advertisement is likely to be ignored: and your flashing image, designed to attract attention, may fall into that trap.
Are you excluding some visitors?
My tests during 2000/2001 included many experienced Internet professionals who spoke English as a second language. They didn't blank the scrolling text, but noticed it: and they found it insulting. Why? Because scrolling text is so much harder to read, and they were annoyed when they saw text that caused them to doubt their language skills.
Moving text is harder to read. As well as any visitor whose first language is not English, you may be excluding:
* people with dyslexia
* people with learning disabilities
* people who are visually impaired and use screen magnifiers
* It can also confuse some screenreaders, used by people who are blind.
That is why the W3C Web Accessibilty Content Guidelines say: 'Ensure that moving, blinking, scrolling, or auto-updating objects or pages may be paused or stopped' (w3.org, 1999). In other words, if you must use motion then make sure the user can stop it easily.