Looks like it could be a difference in how that browser renders the code. Can you post what browser versions you're seeing this problem with? It'll help LawnLad's web person fix the issue.
My $.02 on the site:
I like the really big flower graphic on the index page and in general, the big, rich graphics for each page are excellent (but the pic of the old folks has to go:
LawnLad - Landscaping Services - the old guy looks like you told him he wasn't getting his oatmeal unless he posed for the photo).
There's something about the navigation that's confusing for me - you have a challenge in that there's a great deal of content on the site, and managing to make the navigation easy on a big site is one of the biggest challenges you'll face. That being said, on the index page, so much graphical space is given to the three options on the right that it appears that's all you do. The links in the head of the page seem to get lost relative to those big graphic links.
You've got a really nifty icon group to define the different kinds of services you provide, but I only get introduced to them together if I happen to click MyYARD. Those icons and the content each section covers seems important enough that a graphical link should appear somewhere prominent on the home page, not at an incidental location deeper in the site. (Side note on the icons - every time I look at the red turf icon I think it's a fire safety or fire suppression section - red with flames. Maybe a light green icon instead of red?)
Design services page - the bronze/silver/gold graphic does not line up with text below in Firefox 2.0.0.12 or IE7. Nitpicky, but still.
The ability to allow people to click a nice big icon to add a service to the list of things they want an estimate about is a neat feature. However, the MyYARD main page graphic header "Customized Care for your unique needs" somehow doesn't make it obvious what's supposed to happen on that page. Maybe something more descriptive with less promo language would better suit, like MyYARD: Select Your Services. Then in the text below, explain that a person is expected to select among the choices below and submit the information and a LawnLad rep will contact you by the next business day to schedule an appointment. Or whatever. I also think that having your phone number more prominently listed on every page, especially this page, would be beneficial. I don't know if you're trying to funnel your web visitors to this method instead of phone contact - my preference is phone contact, but you may feel differently. Also, making the phone number bigger will allow propective clients to call you right away instead of having to wait for a return call from your office.
You get points for the form submission - telling the visitor exactly what's happening, and after it's submitted, what's going to happen next.
Re: the tabs at the top of interior pages - you might want to rework those - for Firefox I have to click over a word before the tab will even begin to materialize, then again to get to where I want to go. Also, in both browsers the tab appears too slowly. Either make it immediate or near immediate. Effects are nice, but users shouldn't have to wait for navigation.
From an SEO perspective you might consider sprinkling more geospecific terms into your content. You may also want a site map to help search engine spiders to index all your content, especially since it looks like a lot of links are in javascript.
In general, you've got yourself a really nice site that's rich in content and heavy on the web2.0 side. Very nice.