Originally, IMG tags were disabled, in placing an ad AND in replying to an ad. I believe it had something to do with issues created with the server. We are on a different server now. However, the ability to place IMG tags, in a reply, may not be permanent and may change. So, don't rely on it always working...lol. Another option is to directly upload your photos, to the classified software. The software will resize images, automatically, but has it's limitations. With very large images, the software is unable to automatically resize them. For instance, images taken, with my camera, are all taken at the largest memory settings. My images are way too large. I have resized images to the following, and it worked fine.
400X400 pixel dimension
40KB
150X150dpi
I did a "Batch resize" using Photoshop, which is quick and easy, once you learn how to do it...lol. Another program, which is free and easy (no, I'm not describing myself), is IrfanView.
At first, I wasn't too happy with the classified software, and the need to resize and upload photos, as apposed to the ability to post IMG tags. However, after going through the process, while not as easy as posting IMG tags, it's quite painless, with only a couple quick steps involved.
I think, for the majority of members, the photos taken with their cameras, will be small enough for the resizing software to handle. It's those of us, with higher end DSLR, set on the largest files, that will have to resize.
Hope this helps.