If you mean with
than paste this in your CSS
Code
.posttdMessage img {
max-width:450px;
width:expression((this.width>450) ? "450px" : true);
}
.posttdMessage img {
max-height:650px;
height:expression((this.height>650) ? "650px" : true);
you can change size 
We had a tutorial in our forum, but I can't find it 
