How to align search box w/ css max-width with rest of content container?

We try to add shortcode for search box inside of a div. We want to control the max-width of search box 600px using inline style. When we do this, the search box is no longer aligned on the left with the rest of the content in the container on page. The search box moves off to the right. The width is good but there is a white space (margin or padding?) that is to the left of the search box. We try using float:left; but that makes box go too far left. We just want to control the max width of the search box and have it align on the left in the container with the other blocks.