Be sure that you are using the height and width attributes in the tag. If it is set by default, change them to the original size. This could be due to optimization. These attributes are also optional, so if you don't put them, it won't do anything.
I hope this helps!

Always resize your images before uploading. You probably already have some software that can do the job on your computer, if not, download Irfanview.

Also, never use .bmp images on the internet (you have one on the downloads page)