!!BANNERS NOT WORKING!!

I tried making a banner with Cryptic Jasmines code and it was all white so in a sense it worked, but it didn't because the image wouldn't come (i checked like 4 times that everything was correctly done)... I tried using an already made banner and it wouldn't work (but for others it did). PLZ HELP I WANNA BANNER!!! Do u guys have the same problem or is it just me???